AIRInternational audienc

International audienceInsights into the ethanol electro-oxidation reaction mechanism on palladium in alkaline media are presented combining polarization modulation infrared reflec- tion absorption spectroscopy (PM-IRRAS) and density functional theory (DFT) calculations. The synergy between PM-IRRAS and DFT calculations helps to explain why the C− C bond is not broken during ethanol electro-oxidation, and the reaction stops at acetate. Coupling chronoamperometry (CA) with in situ PM-IRRAS enables us to simultaneously identify ethanol electro-oxidation products on the catalyst surface and in the bulk solution. We show that, at lower potential, it is possible to break the C−C bond on Pd/C in alkaline media to form CO2. However, the selectivity is poor, because of competition with the formation of acetate and other side products, which gets worse at higher potentials. DFT computations complete the picture using the computational hydrogen electrode approach. The computations highlight the pivotal role of the CH3CO intermediate that can either undergo a C−C bond scission yielding CO and then CO2 or that can be oxidized toward CH3COO−. The latter is a dead end in the reaction scheme toward CO2 production, since it cannot be easily oxidized nor broken into C1 fragments. However, CH3CO is not the most favored intermediate formed from ethanol electro-oxidation on Pd, hence limiting the production of CO2

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Navigating glycerol electrochemical oxidation roadmap and catalyst selection.

Novel insights in the synthesis–structure–catalytic activity relationships of nanostructured trimetallic Pt–Rh–Sn electrocatalysts for the electrocatalytic oxidation of ethanol are reported. In particular, we identify a novel single-phase Rh-doped Pt–Sn Niggliite mineral phase as the source of catalytically active sites for ethanol oxidation; we discuss its morphology, composition, chemical surface state, and the detailed 3D atomic arrangement using high-energy (HE-XRD), atomic pair distribution function (PDF) analysis, and X-ray photoelectron spectroscopy (XPS). The intrinsic ethanol oxidation activity of the active Niggliite phase exceeded those of earlier reports, lending support to the notion that the atomic-scale neighborhood of Pt, Rh, and Sn is conducive to the emergence of active surface catalytic sites under reaction conditions. In situ mechanistic Fourier transform infrared (in situ FTIR) analysis confirms an active 12 electron oxidation reaction channel to CO₂ at electrode potentials as low as 450 mV/RHE, demonstrating the favorable efficiency of the PtRhSn Niggliite phase for C–C bond splitting

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Herein, we study the effect of adding bismuth to Ni-nanostructured catalysts (Ni x Bi1–x , x = 100–90 at. %) for glycerol electro-oxidation in alkaline solution by combining physiochemical, electrochemical, and in situ infrared spectroscopy techniques, as well as continuous electrolysis with HPLC (high-performance liquid chromatography) product analysis. The addition of small quantities of Bi (<20 at. %) to Ni nanoparticles led to significant activity enhancement at lower overpotentials, with Ni90Bi10 displaying an over 2-fold increase compared to Ni. Small quantities of bismuth actively affected the reaction selectivity of Ni by suppressing the pathways with C–C bond cleavage, hindering the production of carbonate and formate and improving the formation of tartronate, oxalate, and glycerate. Furthermore, the effect of aging on Ni x Bi1–x catalysts was investigated, resulting in structural modification from the Ni–Bi double shell/core structure to Bi decorated on the folded Ni sheet, thus enhancing their activity twice after 2 weeks of aging. NiBi catalysts are promising candidates for glycerol valorization to high-value-added products.

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