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Pt1 enhanced C-H activation synergistic with Ptn catalysis for glycerol cascade oxidation to glyceric acid


Atomic and cluster Pt websites on Cu-CuZrOx

To be particular, the introduction of atomic Pt and cluster Pt websites was achieved by a galvanic substitute response on the floor of Cu nanoparticles (Supplementary Fig. 1a), which had been ready by in situ dissolution from the zirconium/copper blended oxide. In response to the ratio of zirconium and copper of 4.3: 1 from ICP characterization, the precursor is denoted as Cu1Zr4.3O9.6. As proven within the XRD sample (Supplementary Fig. 1b), Cu1Zr4.3O9.6 was recognized as CuZrO3 section in orthorhombic form (JCPDS 43–0953) with no different impurities. The morphology is an agglomerated flakes kind with a tough floor (Supplementary Fig. 2a). Within the H2-TPR (Supplementary Fig. 2b), two noticed H2 consumptions at 176 and 233 oC could possibly be attributed to the discount of Cu-O-Cu and Cu-O-Zr species38, respectively. The discount was carried out below 450 oC with an H2 stream to acquire supported Cu nanoparticles with a partial Cu discount from bulk Cu1Zr4.3O9.6 (Cu-CuZrOx), in line with the Cu 2p core-level X-Ray photoelectron spectroscopy (XPS) spectra (Supplementary Fig. 3a). As proven within the HRTEM pictures (Supplementary Fig. 4a), Cu nanoparticles with a most measurement distribution of round 3.4 nm are well-dispersed on the agglomerated oxide flakes in particle measurement of fifty–100 nm. The Cu (111) aircraft (lattice spacing: 0.209 nm) is resolved (Supplementary Fig. 4b), in keeping with the looks of a tiny reflection of the Cu (111) within the XRD sample (Supplementary Fig. 1b).

Afterward, a galvanic substitute technique was employed to introduce Pt atoms onto the Cu floor with a Pt loading of 0.5 and 0.9 wt% (Supplementary Desk 1). It’s famous from XRD patterns that the Pt substitute made no vital modifications within the crystalline construction with out resolved Pt section (Supplementary Fig. 1b), implying a excessive dispersion diploma of Pt species. In a Pt loading of 0.5 wt% (Fig. 2a), the nanoparticles in a Cu (111) aircraft present a most measurement distribution of round 3.3 nm on the oxide flakes near Cu-CuZrOx (Supplementary Fig. 4a). Within the aberration-corrected high-angle annular darkfield scanning transmission electron microscopy (AC-HAADF-STEM) picture (Fig. 2b), single Pt atoms (pink circle) are situated on Cu (111) planes and no Pt atoms are resolved on the oxide. The STEM-coupled vitality dispersive spectroscopy (EDS) component mapping (Fig. 2c) of Pt (blue), Cu (yellow), Zr (olive), and O (pink) presents a uniform and excessive dispersion of Pt websites on the Cu nanoparticles, confirming the atomically-dispersed Pt website (0.5percentPt1/Cu-CuZrOx). With an elevated Pt loading of 0.9%, no seen Pt nanoparticles are resolved as a substitute of Cu (111) nanoparticles (~3.4 nm) (Fig. 2nd). Demonstrated by AC-HAADF-STEM pictures (Fig. 2e), just a few Pt clusters round 1.2 nm (olive circle) coexist close by the atomic Pt (pink circle) (0.9percentPt1 + Ptn/Cu-CuZrOx). The 3D floor simulation of the marked areas (yellow rectangles) verifies the adjoining spatial distribution of atomic Pt1 and cluster Ptn (Supplementary Fig. 5). Within the brightness depth profiles (Supplementary Fig. 6), a distance between atomic Pt1 and the Ptn cluster for the 2 marked line I and II is set to be ~0.18 and ~0.22 nm, additional confirming the adjoining spatial distribution. Contemplating the bond size (1.439 Å) of the first C-O in glycerol, it offers the likelihood to kind synergistic adsorption of the first C-O on the adjoining atomic Pt1 and cluster Ptn websites as anticipated. The STEM-EDS mappings (Fig. 2f) verify the coexistence of atomic Pt and cluster Pt websites. Further HRTEM and AC-HAADF-STEM pictures are offered in Supplementary Fig. 7.

Fig. 2: Pt dispersion state and coordination configuration.
figure 2

a–f Consultant HRTEM pictures (a, d), AC-HAADF-STEM pictures (b, e), and HADDF-STEM-EDS component mappings (c, f) of 0.5percentPt1/Cu-CuZrOx (a–c) and 0.9percentPt1+Ptn/Cu-CuZrOx (d–f). g Pt L3-edge FT-EXAFS spectra of 0.5percentPt1/Cu-CuZrOx, and 0.9percentPt1+Ptn/Cu-CuZrOx with bulk Pt foil and PtO2 as references. h CO-DRIFTS spectra of Cu-CuZrOx, 0.5percentPt1/Cu-CuZrOx, and 0.9percentPt1+Ptn/Cu-CuZrOx.

Within the Fourier-transformed prolonged X-ray absorption effective construction spectra (FT-EXAFS, Fig. 2g) on the Pt L3-edge, 0.5percentPt1/Cu-CuZrOx reveals one dominant peak within the area round 2.3 Å situated between PtO2 and Pt foil, demonstrating the formation of Pt-Cu coordination in line with the references36,37. As fitted (Supplementary Desk 2), solely 8.3 Pt-Cu coordination was recognized with none Pt-Pt or Pt-O coordination detected. Whereas, 0.9percentPt1 + Ptn/Cu-CuZrOx presents a wider peak within the area round 2.3 Å with an uneven shoulder peak within the area round 2.6 Å, comparable to Pt-Cu and Pt-Pt coordination construction with fitted 6.1 Pt-Cu and three.0 Pt-Pt coordination, confirming the coexistence of atomic Pt1 and cluster Ptn. In situ CO-absorbed diffuse reflectance infrared Fourier remodel spectroscopy measurements (CO-DRIFTS, Fig. 2h) had been carried out to probe the atomic geometry configuration of Pt websites on the Cu floor. On Cu-CuZrOx as management, a weak and broad absorption band at 2099 cm−1 related39,40 with chemisorbed CO on Cu0 species seems. On 0.5percentPt1/Cu-CuZrOx, two deconvoluted bands by multi-peaks Gaussian becoming are noticed at 2105 and 2062 cm−1, respectively. By comparability to Cu-CuZrOx, the previous band is attributed39,40 to the chemisorbed CO absorption on Cu0 species in an electron-deficient state because of the Cu-Pt coordination. The latter is related41,42,43 with the linearly-bonded CO on atomic Pt. On 0.9percentPt1 + Ptn/Cu-CuZrOx, in addition to the bands for CO adsorbed on Cu0 species (2102 cm−1) and CO linearly-adsorbed on atomic Pt (2065 cm−1), two bands at 2023 and 1853 cm−1 attributed42,43 to CO linearly- and bridged-adsorbed on Pt clusters are resolved, respectively.

Further PtCu bimetallic catalysts possessing solely Pt clusters (0.9percentPtn/Cu-CuZrOx) and distinctive bulk PtCu alloy nanoparticles (0.9percentPtCu-CuZrOx) had been designed. 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx had been ready by incipient wetness impregnation to introduce PtCl62- onto Cu-CuZrOx or CuZrOx adopted by discount. For 0.9percentPtn/Cu-CuZrOx, no seen Pt nanoparticles are resolved as a substitute of Cu nanoparticles in a particles measurement of three.4 nm (Fig. 3a). Pt clusters round 1.2 nm (olive circle) are noticed on Cu (111) planes with out seen atomic Pt, aside from on the oxide floor (Fig. 3b). For 0.9percentPtCu-CuZrOx, PtCu alloy (111) nanoparticles with a particle measurement of three.5 nm had been obtained (Fig. 3c), and no seen particular person Pt atoms are distinguished within the AC-HAADF-STEM picture (Fig. 3d). In R-spaced FT-EXAFS spectra (Fig. 3e), in addition to Pt-Cu coordination (2.3 Å), 0.9percentPtn/Cu-CuZrOx possesses rather more Pt-Pt coordination than 0.9percentPt1 + Ptn/Cu-CuZrOx within the gentle of the bigger uneven shoulder peak within the area round 2.6 Å. 0.9percentPtCu-CuZrOx reveals one dominant peak (2.3 Å) with a tiny shoulder peak (2.6 Å), indicating Pt-Cu as the principle Pt coordination with a small quantity of Pt-Pt coordination. Furthermore, no resolved PtO coordination is noticed. As a comparability for 0.9percentPt1 + Ptn/Cu-CuZrOx in 6.1 Pt-Cu and three.0 Pt-Pt coordination, 4.1 Pt-Cu and a pair of.9 Pt-Pt coordination are recognized for 0.9percentPtn/Cu-CuZrOx, and 4.1 Pt-Cu and a pair of.3 Pt-Pt coordination for 0.9percentPtCu-CuZrOx, respectively (Supplementary Desk 2). CO-DRIFTS spectra of the physically-mixed 0.5percentPt1/Cu-CuZrOx and 0.9percentPtn/Cu-CuZrOx had been collected as management (Supplementary Fig. 8). The CO linearly-adsorbed bands on Pt1 (2062 cm−1) and cluster Ptn (2033 cm−1) on the physically-mixed 0.5percentPt1/Cu-CuZrOx and 0.9percentPtn/Cu-CuZrOx shift to 2065 and 2023 cm−1 on 0.9percentPt1 + Ptn/Cu-CuZrOx with an elevated discrepancy (Fig. 2h), which could possibly be brought on by the CO molecule conjugation44 on adjoining atomic and cluster Pt in 0.9percentPt1 + Ptn/Cu-CuZrOx.

Fig. 3: Modulation on Pt coordination configuration and digital state.
figure 3

a–d Consultant HRTEM and AC-HAADF-STEM pictures of 0.9percentPtn/Cu-CuZrOx (a, b) and 0.9percentPtCu-CuZrOx (c, d). e–g Pt L3-edge FT-EXAFS spectra (e), normalized XANES spectra (f), and the valence state evaluation (g) of 0.9percentPt1+Ptn/Cu-CuZrOx, 0.9percentPtn/Cu-CuZrOx, and 0.9percentPtCu-CuZrOx with bulk Pt foil and PtO2 as references.

Within the Pt L3-edge spectra of X-ray absorption near-edge construction spectra (XANES, Fig. 3f), every PtCu shows a white line depth under Pt foil, indicative of electron-rich Pt (Ptδ-). As enlarged within the inset, with the reference of Pt foil, the depth of the pink line signifies 0.9percentPt1 + Ptn/Cu-CuZrOx is probably the most negative-charged, and subsequently, 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx. Within the first-derivative of absorption edge in normalized XANES spectra, the absorption threshold (E0) was obtained (Supplementary Fig. 9), which was then plotted as a operate of the oxidation state (Fig. 3g). The Ptδ- valence state has been quantified in a δ worth of 1.85, 1.13, and 0.44 for 0.9percentPt1 + Ptn/Cu-CuZrOx, 0.9percentPtn/Cu-CuZrOx, and 0.9percentPtCu-CuZrOx respectively from the linear becoming end in gentle of the PtO2 and Pt foil. In Cu 2p3/2 XPS spectra (Supplementary Fig. 3a), the height assigned38 to Cu0 or CuI species shifts to decrease binding vitality after Pt loading, indicating an electron donation from Cu to Pt atoms. Within the Cu X-ray excited Auger electron spectroscopy (XAES) spectra (Supplementary Fig. 3b), the kinetic vitality of the height assigned45 to Cu0 species shifts to low vitality in comparison with Cu-CuZrOx, confirming the electron-deficient state for Cu within the Pt-Cu bonds, in accordance with the XANES spectra evaluation (Fig. 3f, g).

Cascade synergistic activation by atomic Pt1 and cluster Ptn websites

The activation of glycerol has been first investigated by in situ FT-IR spectra after the adsorption of 1-propanol for 30 min adopted by desorption, which possesses solely major O-H bonds (Fig. 4). On 0.9percentPt1 + Ptn/Cu-CuZrOx (Fig. 4a and Supplementary Desk 3), in addition to the bands attributed46,47,48 to adsorbed bidentate 1-propanol and propoxy (marked in magenta), adsorbed monodentate propoxy (marked in blue), and η1-adsorbed propanal (marked in pink), the bands at 2740, 1275, and 1350 cm−1 assigned46,47,48 to ν(CH), ν(C-O) and δ(CH) of η2-adsorbed propanal (marked in olive) seem. The corresponding adsorption fashions labeled in the identical coloration are additionally displayed under. Because the desorption time elevated, the bands step by step lower aside from the η2-adsorbed mode, which is inferred to be steady in such a synergistic activation. Whereas on 0.9percentPtn/Cu-CuZrOx (Fig. 4b) or 0.9percentPtCu-CuZrOx (Fig. 4c), comparable absorption bands with weakened depth for adsorbed 1-propanol, propoxy species, and η1-adsorbed propanal seem, besides that no bands for η2-adsorbed propanal are resolved. Mixed with the digital state evaluation, Ptδ--Cu bonds are accountable for the dehydrogenation of the C-H bonds as anticipated and the growing electron-rich state in 0.9percentPt1 + Ptn/Cu-CuZrOx promotes the activation of the C-H bonds. Furthermore, by evaluating the realm ratio of ν(C-O) and ν(C-OH) of the adsorbed bidentate 1-propanol (marked in magenta), 0.9percentPtn/Cu-CuZrOx reveals superior O-H activation past 0.9percentPt1 + Ptn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx, confirming that the Pt-Pt bonds are accountable for the dehydrogenation of the first O-H bonds to propoxy and extra Pt-Pt coordination (Supplementary Desk 2) is most well-liked. As a management, on 0.5percentPt1/Cu-CuZrOx (Fig. 4d), virtually no propoxy and propanal species had been noticed aside from the adsorbed non-dissociated 1-propanol species.

Fig. 4: The activation of the first O-H and C-H bonds.
figure 4

In situ FT-IR spectra after the adsorption of 1-propanol for 30 min adopted by desorption at desorption occasions of 1, 5, 10, 15, and 20 min (from prime to backside) on 0.9percentPt1+Ptn/Cu-CuZrOx (a), 0.9percentPtn/Cu-CuZrOx (b), 0.9percentPtCu-CuZrOx (c), and 0.5percentPt1/Cu-CuZrOx (d). The simulated adsorption fashions are displayed comparable to the absorption band labeled in the identical coloration.

Then the glycerol activation on atomic Pt1 and cluster Ptn websites has been investigated (Fig. 5a and Supplementary Desk 4). Taking pristine glycerol as reference (Supplementary Fig. 10a), on 0.9percentPt1 + Ptn/Cu-CuZrOx two sturdy absorption bands at 1068 and 1054 cm−1 attributed49,50,51,52 to major ν(C-O) of bidentate and monodentate dissociated glycerol (marked in magenta), a powerful band at 1099 cm−1 to49,50,51,52 the secondary ν(C-OH) of non-dissociated glycerol (marked in blue), and a tiny band at 1152 cm−1 to49,50,51,52 non-dissociated glycerol with secondary O-H group forming hydrogen bonds on the steel oxides (marked in blue) seem, indicating the dominance on the dissociated activation of the first O-H bands. Moreover η1-adsorbed GLAD (marked in pink), the bands at 2713, 1337, and 1186 cm−1 assigned53,54 to ν(CH), δ(CH), and ν(C-O) of η2-adsorbed GLAD (marked in olive) seem. No seen activation of the secondary C-H bonds to dihydroxyacetone51 has been detected. Whereas on 0.9percentPtn/Cu-CuZrOx or 0.9percentPtCu-CuZrOx, no apparent bands for η2-adsorbed GLAD are resolved, and solely weakened major O-H and C-H bond activation are detected. Extra H-bonded secondary ν(C-OH) species on 0.9percentPtCu-CuZrOx are noticed. As a management, on 0.5percentPt1/Cu-CuZrOx, solely H-bonded secondary ν(C-OH) species seem with none dissociated GLAD detected. Subsequently, the dominant activation of major O-H and C-H bonds of glycerol in η2-GLAD mode on atomic Pt1 and cluster Ptn websites has been recognized, in keeping with the in situ FT-IR spectra of the 1-propanol adsorption. As well as, the looks of ν(OCO) in glycerate (marked in wine) could possibly be attributed51 to the adsorption of shaped C=O on steel and the steel oxides.

Fig. 5: The adsorption and the activation of glycerol and glyceraldehyde.
figure 5

In situ FT-IR spectra of the adsorption of glycerol (a) and glyceraldehyde (b) on 0.9percentPt1+Ptn/Cu-CuZrOx, 0.9percentPtn/Cu-CuZrOx, 0.9percentPtCu-CuZrOx, and 0.5percentPt1/Cu-CuZrOx with the simulated adsorption fashions comparable to the absorption bands labeled in the identical coloration. Schematic illustrations of glyceraldehyde adsorption in η2-GLAD mode over Pt1 + Ptn websites and Ptn websites are additionally displayed.

The activation of the aldehyde group has been first investigated by in situ FT-IR spectra of the adsorption of acetaldehyde (Fig. 6). On 0.9percentPt1 + Ptn/Cu-CuZrOx (Fig. 6a and Supplementary Desk 5), the bands at 1760, 1747 and 1730 cm−1 assigned55,56,57 to ν(C=O) of η1-adsorbed acetaldehyde (marked in pink) and bands at 1275 and 1352 cm−1 assigned55,56,57 to ν(C-O) and δ(CH) of η2-adsorbed acetaldehyde (marked in olive) each seem. On 0.9percentPtn/Cu-CuZrOx (Fig. 6b), comparable absorption bands for η1– and η2-adsorbed acetaldehyde with sharply-weakened depth are noticed, besides {that a} broad band round 3000 cm−1 related55 with the coupling merchandise of adsorbed acetaldehyde seems (marked in darkish yellow). Because the desorption time elevated, in addition to the band at 1352 cm−1 assigned55,56,57 to δ(CH) in η2-acetaldehyde species on sole Ptn websites, a band at 1345 cm−1 assigned to a weaker δ(CH) additionally seem, which could possibly be generated by the stronger Pt-C interplay on extra electron-deficient Pt1 websites in 0.9percentPt1 + Ptn/Cu-CuZrOx. It’s envisaged that the era of η2-adsorbed acetaldehyde on atomic Pt1 and cluster Ptn websites make the C=O activation a lot quicker and inhibits the facet coupling response. As well as, the ν(OCO) bands attributed55 to the C=O adsorption on steel websites and oxygen of steel oxides (marked in wine) additionally seem. For GLAD activation (Fig. 5b), taking pristine GLAD as reference (Supplementary Fig. 10b), η1– (marked in pink) and η2-adsorbed (marked in olive) GLAD species53,54 are each noticed on 0.9percentPt1+Ptn/Cu-CuZrOx, 0.9percentPtn/Cu-CuZrOx, and 0.9percentPtCu-CuZrOx. On 0.9percentPt1 + Ptn/Cu-CuZrOx, η2-adsorbed GLAD are dominant adsorbed species. Whereas on 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx, η1-adsorbed GLAD species seem as predominant adsorption. It’s value noting that the η2-GLAD ν(C-O) band (crammed in olive) at 1196 cm−1 on 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx shows an apparent red-shift to 1183 cm−1 on 0.9percentPt1 + Ptn/Cu-CuZrOx (Fig. 5b, inset), indicating a weaker ν(C-O) within the η2-GLAD on Pt1 and Ptn websites than that on sole Ptn websites, which could possibly be attributed to the stronger Pt-C interplay on extra electron-deficient Pt1 websites in 0.9percentPt1 + Ptn/Cu-CuZrOx, in accordance with the acetaldehyde adsorption. It offers experimental proof on the formation of η2-adsorbed GLAD by the synergistic activation of atomic Pt1 and cluster Ptn websites. Extra glycerate species (marked in wine) are noticed on 0.9percentPtn/Cu-CuZrOx, inferring that η1-adsorbed GLAD species facilitate the formation of ν(OCO) adsorption on steel and oxides. For management, 0.5percentPt1/Cu-CuZrOx has solely η1-adsorbed GLAD species. In every case, no apparent C2-OH and C3-OH activation in GLAD is detected.

Fig. 6: The activation of the C=O bonds in aldehyde.
figure 6

In situ FT-IR spectra after the adsorption of acetaldehyde for 30 min adopted by desorption at desorption occasions of 1, 5, 10, 15, and 20 min (from prime to backside) on 0.9percentPt1+Ptn/Cu-CuZrOx (a), and 0.9percentPtn/Cu-CuZrOx (b), with enlarged spectra between 1360 and 1300 cm−1 crammed in olive shading (c). The simulated adsorption fashions are displayed comparable to the adsorption band labeled in the identical coloration.

The desorption of carboxyl teams has been investigated by in situ FT-IR spectra after the adsorption of propionic acid adopted by desorption (Fig. 7 and Supplementary Desk 7). The adsorption of the carboxyl teams on the steel clusters or nanoparticles might end in monodentate and bidentate configuration contemplating the floor steel atom association58. On 0.9percentPt1 + Ptn/Cu-CuZrOx (Fig. 7a), a weak band at 1597 cm−1 recognized48,57,59 as νa(OCO) in monodentate configuration (marked in blue) and the bands at 1530 and 1436 cm−1 recognized48,57,59 as νa(OCO) and νs(OCO) in bridging bidentate configuration (marked in magenta) on cluster Ptn seem. On 0.9percentPtn/Cu-CuZrOx (Fig. 7b), intensified νa(OCO) absorption bands at 1597 and 1533 cm−1 in each monodentate and bridging bidentate adsorption on cluster Ptn are recognized, demonstrating sturdy adsorption of the carboxyl teams. On 0.9percentPtCu-CuZrOx (Fig. 7c), solely νa(OCO) absorption band in bridging bidentate adsorption on cluster Ptn is noticed. 0.9percentPt1 + Ptn/Cu-CuZrOx with much less Pt-Pt coordination amount in the same Pt-Pt coordination quantity with 0.9percentPtn/Cu-CuZrOx reveals higher desorption of carboxyl teams. As a management, on pristine Cu-CuZrOx (Fig. 7d), solely tiny absorption bands assigned58 to the vapor propionic acid had been detected. Mixed with the GLAD adsorption (Fig. 5b), it’s concluded that 0.9percentPt1 + Ptn/Cu-CuZrOx reveals each higher activation of the aldehyde group and desorption of the carboxy group originated from the synergistic catalysis by atomic Pt1 and cluster Ptn websites, which is envisaged to facilitate the direct transformation from GLAD to GLYA.

Fig. 7: The desorption habits of carboxyl teams.
figure 7

In situ FT-IR spectra after the adsorption of propionic acid for 30 min adopted by desorption at desorption occasions of 1, 5, 10, 15, and 20 min (from prime to backside) on 0.9percentPt1+Ptn/Cu-CuZrOx (a), 0.9percentPtn/Cu-CuZrOx (b), 0.9percentPtCu-CuZrOx (c), and Cu-CuZrOx (d) with simulated adsorption fashions displayed in the identical coloration.

Cascade synergistic catalysis throughout in situ floor response

In situ time-resolved FT-IR spectra of 0.9percentPt1 + Ptn/Cu-CuZrOx on publicity to 1-propanol at 60 oC in a stream of O2 and H2O had been recorded to additional elucidate the cascade synergistic catalysis and the evolution of floor adsorbed intermediates within the oxidation of glycerol to GLYA (Fig. 8a). The bands between 1600~1500 cm−1 assigned to the ν(OCO) of the adsorbed propionic acid in bridging bidentate configuration seem and step by step enhance with on-steam time, accompanied with the looks of ν(C=O) band of carboxyl teams since 15 min. It signifies that 1-propanol could possibly be transformed to propionic acid over 0.9percentPt1 + Ptn/Cu-CuZrOx within the presence of O2 and H2O. With on-steam time, the realm ratio of ν(C-O) at 1138 cm−1 of the adsorbed monodentate 1-propanol (marked in blue) to ν(C-OH) at 1165 cm−1 of the adsorbed monodentate propoxy (marked in cyan) step by step will increase, however that of the adsorbed monodentate 1-propanol should not so seen (marked in magenta). With on-steam time, the realm ratio of the entire monodentate ν(C-O) and ν(C-OH) (1138 and 1165 cm−1) to the entire bidentate ones (1053 and 1066 cm−1) step by step decreases. It evidences that the formation of propionic acid is originated from the adsorbed monodentate 1-propanol. The ν(CH), δ(CH3), and ν(C-O) bands of η2-adsorbed propanal (marked in olive) are clearly resolved with out η1-adsorbed propanal bonds, confirming the synergistic activation of atomic Pt1 and cluster Ptn on the C-H and O-H bonds, and demonstrating the η2-adsorbed propanal because the intermediates within the subsequent oxidation course of to propionic acid. Extra importantly, the realm ratio of ν(C-O) in propoxy at 1138 cm−1 (marked in blue) to ν(C-O) in η2-mode propanal at 1295 cm−1 (marked in olive) exceptional elevated with on-steam time, indicating that the synergistic activation pathway is O-H activation on the Ptn cluster adopted by the C-H activation on the atomic Pt1 websites. The schematic illustration of the doable floor response course of has been displayed in Fig. 8b. In situ XANES spectroscopy, which is delicate for measuring the chemical states of Pt and Cu, was carried out to research their modifications through the catalytic response (Supplementary Fig. 11). It’s discovered that the introduction of glycerol on 0.9percentPt1 + Ptn/Cu-CuZrOx results in a definite low-energy shift of the white line peak in Pt L3-edge XANES spectra (Supplementary Fig. 11a). Then the publicity to O2 make the white line step by step return to the same stage of the contemporary catalyst. As for the Cu Ok-edge XANES spectra after the sequential publicity to glycerol answer and O2 stream (Supplementary Fig. 11b), no seen change of the Cu adsorption edge has been noticed, implying that no apparent impact on floor Cu species has been detected within the oxidation on this work. Cu species has been inferred to play a job within the electron donation to Pt atom to kind Ptδ--Cu coordination selling the C-H activation of glycerol through the oxidation.

Fig. 8: Schematic diagram of the response pathway throughout in situ floor response.
figure 8

a In situ time-resolved FT-IR spectra of 0.9percentPt1+Ptn/Cu-CuZrOx on publicity to 1-propanol at 60 oC was recorded within the presence of O2 and H2O. From backside to prime: 1, 5, 10, 15, 20, 25, and 30 min. Adsorbates had been launched to the chamber by effervescent the 1-propanol aqueous answer with O2/Ar (v:v = 1:5) stream (40 mL/min). b Proposed floor response course of on the oxidation of 1-propanol to propionic acid.

The selective oxidation of glycerol on 0.9percentPt1 + Ptn/Cu-CuZrOx utilizing 18O2 and H218O had been carried out, respectively, to establish the reactive oxygen species (Supplementary Fig. 12), which had been reported to take part within the oxidation course of. With 18O2 labeling, 18O was not noticed within the merchandise of glycerol oxidation (Supplementary Fig. 12a). With H218O labeling, the mass spectrum exhibits that one or two 18O atoms had been integrated into GLYA as the principle product with a small quantity of GLAD or DHA as by-products (Supplementary Fig. 12b). Combining with the earlier experiences29,60, it could possibly be concluded that activated O2 and H2O had been integrated to kind peroxide (OOH) and OH to summary adsorbed C-H and O-H bonds, lastly producing H2O2 and H2O (Supplementary Fig. 12c). To confirm the H2O2 era, the contemporary response answer and reference samples had been blended with a blended answer (P) containing phosphate buffer, N,N-diethylbenzene-1,4-diamine sulfate (DPD), and horseradish peroxidase (POD)61 to look at the change in coloration (Supplementary Fig. 12d). The answer coloration for the contemporary response answer with P answer is visibly darker than that for every particular person product with P, confirming the H2O2 institution within the glycerol oxidation.

Atomic Pt1 enhanced C-H activation synergistic with cluster Ptn catalysis to advertise glycerol conversion and GLYA selectivity

Within the selective oxidation of glycerol in an ebullated mattress with an O2 stream of 30 mL/min at 60 oC, 0.9percentPt1 + Ptn/Cu-CuZrOx catalyzed the conversion of glycerol to GLYA with a selectivity of 80.2 ± 0.2% at a glycerol conversion of 90.0 ± 0.1% in 8 h (Fig. 9 and Supplementary Desk 8). Over 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx, a GLYA selectivity of 66.9% at a glycerol conversion of 85.6%, and a GLYA selectivity of 60.6% at a glycerol conversion of 65.0% had been achieved. Whereas 0.5percentPt1/Cu-CuZrOx solely provides a really low conversion of three.7% with a GLYA selectivity of 64.1% (Supplementary Fig. 13a) and don’t change with time. As a management, the exercise of Cu-CuZrOx is negligible (0.4%) with oxalic acid (OA) and formic acid (FA) as principal merchandise (Supplementary Fig. 13b). It signifies that the cooperation of atomic Pt1 with cluster Ptn promotes the glycerol conversion (Fig. 9a). Within the profile of the response charge in the direction of the Pt valence state (Fig. 9b), an excellent linear relationship between the exercise and the Pt electron-rich state shows, additional confirming the improved C-H activation by atomic Pt1 results in promoted glycerol conversion. When 0.9percentPt1+Ptn/Cu-CuZrOx was pretreated by N2O to poison the floor Cu websites (0.9percentPt1 + Ptn/Cu-CuZrOx-N2O), sharply-declined glycerol conversion to 70.0% additional supporting the improved C-H activation by atomic Pt1 websites (Supplementary Desk 8). To make sure that the catalytic experiments had been carried out below the regime of kinetic management, Mears and Weisz–Prater analyses62,63,64,65 had been employed to research the mass switch based mostly on the response charges in our work (Supplementary Desk 9). The calculated values of the Mears criterion are 7.74 × 10−5, 5.57 × 10−5, and 4.31 × 10−5 on 0.9percentPt1 + Ptn/Cu-CuZrOx, 0.9percentPtn/Cu-CuZrOx, and 0.9percentPtCu-CuZrOx, respectively, far smaller than 0.15, implying that exterior mass switch results will be uncared for. The calculated values of the Weisz–Prater Criterion are 2.96 × 10−9, 2.32 × 10−9, and 1.18 × 10−9 on 0.9percentPt1 + Ptn/Cu-CuZrOx, 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx, respectively, far smaller than 1, implying that inner mass switch results will also be uncared for.

Fig. 9: Pt digital construction and the catalytic analysis.
figure 9

a–c Within the selective oxidation of glycerol, time-dependent glycerol conversion (a), profile of glycerol conversion charge with Pt valence state (b), and comparability of product selectivity at comparable glycerol conversion (c). d–f Within the selective oxidation of GLAD, time-dependent GLAD conversion (d), comparability of product selectivity (e), and profiles of GLAD conversion charge and H2O2 manufacturing charge with Pt valence state (f). Response circumstances: ebullated mattress, 15 mL of substrate aqueous answer (0.1 mol L−1), substrate/Pt (mol/mol) = 300, 60 oC, O2 stream of 30 mL/min. Cu-CuZrOx was enter utilizing the identical mass with 0.9percentPt1 + Ptn/Cu-CuZrOx.

Over 0.9percentPt1+Ptn/Cu-CuZrOx, the GLYA selectivity holds at 80.4% alongside the growing time, with a small quantity of glyceraldehyde (5.3%) and DHA (9.5%) (Supplementary Fig. 14a). No apparent GLAD accumulation or transformation is noticed together with the growing response time, indicating a quick conversion from GLAD to GLYA. GLYA selectivity over 0.9percentPtn/Cu-CuZrOx barely will increase together with the response time and reaches 66.7% at 4 h with 10.6% GLAD, 11.9% of DHA, and 5.4% of acetic acid (HAc) (Supplementary Fig. 14b). Over 0.9percentPtCu-CuZrOx, it step by step will increase and reaches 60.6% at 6 h with 9.5% of GLAD, 12.6% of DHA, and 9.6% of HAc (Supplementary Fig. 14c). An apparent transformation from GLAD to GLYA is noticed together with the growing time over 0.9percentPtn/Cu-CuZrOx and 0.9percentPtCu-CuZrOx, demonstrating a lot slower charge of the GLAD oxidation to GLYA than that from glycerol to GLAD. At comparable glycerol conversion (Fig. 9c), the GLYA selectivity over 0.9percentPtn/Cu-CuZrOx (66.7%) and 0.9percentPtCu-CuZrOx (60.6%) is way decrease than that over 0.9percentPt1 + Ptn/Cu-CuZrOx (80.2 ± 0.2%), ascribed to the poorer transformation from GLAD to GLYA and extra C-C cleavage to HAc. Over 0.9percentPt1 + Ptn/Cu-CuZrOx-N2O, a pointy decline within the GLYA selectivity to 67.9% with an elevated GLAD selectivity of 18.2% confirms that Ptδ--Cu bonds play a key position within the C-H activation from GLAD to GLYA. Furthermore, it’s value noting that comparable DHA selectivity over 0.9percentPt1 + Ptn/Cu-CuZrOx (10.0 ± 0.5%), 0.9percentPtn/Cu-CuZrOx (11.9%), and 0.9percentPtCu-CuZrOx (12.6%) was detected, respectively (Supplementary Desk 8). In response to our current work66, an isotope labeling experiment utilizing deuterium labeling of glycerol within the secondary C-H bond was carried out and DHA was side-produced from the direct activation of secondary O-H bonds in glycerol (Supplementary Fig. 15).

The selective oxidation of GLAD to GLYA was then carried out. A GLAD conversion of 98.0% with a GLYA selectivity of 93.1% over 0.9percentPt1 + Ptn/Cu-CuZrOx at 5 h is achieved, rather more environment friendly than that over 0.9percentPtn/Cu-CuZrOx (71.1% of GLAD conversion with 81.2% of GLYA selectivity) and 0.9percentPtCu-CuZrOx (65.2% of GLAD conversion with 64.9% of GLYA selectivity), respectively (Fig. 9d, e). It might nicely account for the regular GLYA selectivity over 0.9percentPt1+Ptn/Cu-CuZrOx within the cascade oxidation of glycerol to GLYA. Within the profile of the response charge in the direction of the Pt valence state (Fig. 9f, stable ball), elevated with the Pt valence state, the response charge sharply will increase, implying that the GLAD conversion primarily relies on the electron-rich state of the C-H activation in addition to the insertion of O-H bonds. The synergistic activation of GLAD in η2-mode and the improved C-H activation are moderately inferred to reinforce the GLAD conversion. As well as, the established H2O2 within the response was then quantified utilizing KMnO4 titration after which was associated to the Pt valence state (Fig. 9f, hole ball). The same enhance tendency is displayed together with the growing Pt valence state. It demonstrates that the generated reactive oxygen species throughout the entire oxidation course of had been adequate to perform the cascade oxidation. Benefited from the prevalence of each the adsorption of aldehyde and the desorption of carboxylic acid in situ FT-IR spectra (Figs. 57), the improved GLYA selectivity could possibly be moderately achieved.

The selective oxidation of glycerol over 0.9percentPt1 + Ptn/Cu-CuZrOx below tailor-made response circumstances has been carried out (Supplementary Desk 10). Underneath the O2 stream charge of 30 (entry 1), 60 (entry 2), or 150 mL/min (entry 3), the glycerol conversion and GLYA selectivity maintain on the similar worth, additional confirming the absence of the mass switch. Underneath the glycerol/Pt (mol/mol) of 300 (entry 1), 500 (entry 4), 650 (entry 5), and 1000 (entry 6), the glycerol conversion step by step declined at an analogous response charge between 157–160 molgl molPt−1 h−1 and the GLYA selectivity barely will increase with decreased GLAD and DHA selectivity. Underneath the glycerol/Pt (mol/mol) of 1000, a GLYA selectivity of 84.4% at a glycerol conversion of 79.8% is obtained. Furthermore, below elevated glycerol focus to 0.3 M, a GLYA selectivity of 82.3% at a declined glycerol conversion of 80.0% is obtained with the response charge holding at 158 molgl molPt−1 h−1. No apparent change within the response intermediates as a result of catalyst poisoning was detected. Over 0.9percentPt1 + Ptn/Cu-CuZrOx, the obtained glycerol conversion and GLYA selectivity within the selective oxidation of glycerol to GLYA at 60 oC below atmospheric stress in an O2 stream, to the very best of our data, is larger than the experiences below the identical situation (Supplementary Desk 11).

The reusability of 0.9percentPt1 + Ptn/Cu-CuZrOx was then examined below the glycerol/Pt (mol/mol) of 1000 (Supplementary Fig. 16). The catalyst was separated by easy filtration and subsequently used with none remedy. Each the glycerol conversion and the GLYA selectivity are nicely preserved after 5 runs (Supplementary Fig. 16a). Virtually no Pt leaching from the stable catalyst or no Pt presence within the spent response answer was detected (Supplementary Fig. 16b). 4.7 and three.8% of Cu and Zr had been detected to leach from the stable in 5 runs. The overall Cu and Zr leached into the collected spent response answer for 5 runs had been decided to be 4.2 and three.6%, in keeping with the loss in a stable catalyst. The HRTEM pictures, the AC-HAADF-STEM pictures, and the Pt L3-edge FT-EXAFS spectra of the spent 0.9percentPt1 + Ptn/Cu-CuZrOx (Supplementary Figs. 17 and 18) point out that the dispersion, the coordination and the digital state of Pt energetic websites have been nicely retained in comparison with the contemporary catalyst. Within the Cu 2p3/2 XPS spectra and X-ray induced Cu Auger electron spectra of the spent Pt1 + Ptn/Cu-CuZrOx (Supplementary Fig. 19), the digital state of Cu species shows no apparent change. The floor Pt/Cu molar ratio will increase from 1/15 within the contemporary 0.9percentPt1 + Ptn/Cu-CuZrOx to 1/14 and the CuII/Cu0/I molar ratio decreases from 1/4 to 1/5. Contemplating no Pt leaching is detected, the slight Cu leaching is deduced to be originated from the CuII species by the chelation of acid manufacturing.

In conclusion, this work proposes and confirms a cascade synergistic catalysis of atomic Pt1 and cluster Ptn for the cascade oxidation of glycerol to GLYA, using Pt1 + Ptn/Cu-CuZrOx built-in by atomic Pt1 and cluster Ptn. In comparison with the cluster/nanoparticles Pt websites, the improved C-H activation within the cascade oxidation by the atomic Pt1 within the synergistic catalysis contributes to the simultaneous excessive glycerol exercise and excessive GLYA selectivity. This work not solely paves an alternate technique for selling the cascade catalysis by engineering the floor steel energetic websites but additionally presents a inexperienced and environment friendly value-added routine from glycerol as industrial by-products. Additional work in our lab continues to be underway to discover multi-synergistic catalysis to additional understand the correct activation within the major place of polyols.

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