Double pulse voltammetric study of the IT-CeqC mechanism underlying the oxygen reduction and hydrogen evolution reactions at liquid/liquid interfaces

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Double pulse voltammetric study of the IT-CEqC mechanism Underlying the oxygen reduction and hydrogen evolution reactions at liquid/liquid interfaces

International audienc

Kinetic Influence of Surface Charge Transfer Reactions Preceded by Non-Electrochemical Processes on the Response in Cyclic Voltammetry

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Double pulse voltammetric study of the IT-CEqC mechanism Underlying the oxygen reduction and hydrogen evolution reactions at liquid/liquid interfaces

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Nanocatalyseurs Cu100-xPdx pour la réduction électrochimique du CO2

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Copper-Palladium Nanoelectrocatalysts for Carbon Dioxide Reduction, International Symposium on Electrocatalysis

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Double pulse voltammetric study of the IT-CEqC mechanism Underlying the oxygen reduction and hydrogen evolution reactions at liquid/liquid interfaces

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Selective Catalytic Electroreduction of CO2 at Silicon Nanowires (SiNWs) Photocathodes Using Non-Noble Metal-Based Manganese Carbonyl Bipyridyl Molecular Catalysts in Solution and Grafted onto SiNWs

International audienceThe electrocatalytic redn. of CO2 to CO in hydroorg. medium has been investigated at illuminated (λ \textgreater 600 nm; 20 mW cm-2) hydrogen-terminated silicon nanowires (SiNWs-H) photocathodes using three Mn-based carbonyl bipyridyl complexes as homogeneous mol. catalysts ([Mn(L) (CO)3(CH3CN)](PF6) and [Mn(bpy) (CO)3Br] with L = bpy = 2,2'-bipyridine and dmbpy = 4,4'-dimethyl-2,2'-bipyridine). Systematic comparison of their cyclic voltammetry characteristics with those obtained at flat hydrogen-terminated silicon and traditional glassy carbon electrodes (GCE) enabled us to demonstrate the superior catalytic efficiency of SiNWs-H in terms of cathodic photocurrent densities and overpotentials. For example, the photocurrent densities measured at -1.0 V vs SCE for [Mn(bpy) (CO)3(CH3CN)](PF6) at SiNWs-H exceeded 1.0 mA cm-2 in CO2-satd. CH3CN + 5% vol./vol. H2O, whereas almost zero current was measured at this potential at GCE. Such characteristics have been supported by the energetic diagrams built for the different SiNWs\textbarMn-based catalyst interfaces. The fill factor FF and energy conversion efficiency η calcd. under catalytic conditions were higher for [Mn(bpy or dmbpy) (CO)3(CH3CN)](PF6) (FF = 0.35 and 0.34; η = 3.0 and 2.0%, resp.). Further preparative-scale electrolysis at SiNWs-H photocathode with Mn-based complex catalysts in electrolytic soln. evidenced the quant. conversion of CO2 to CO with a higher stability of the [Mn(dmbpy) (CO)3(CH3CN)](PF6) complex. Finally, in order to develop technol. viable electrocatalytic devices, the elaboration of SiNWs-H photoelectrodes modified with a Mn-based complex has been successfully achieved from an electropolymerizable catalyst, and it was shown that the electrocatalytic activity of the complex was retained after immobilization

Mesopore Formation and Silicon Surface Nanostructuration by Metal-Assisted Chemical Etching With Silver Nanoparticles

International audienceThis article presents a study on Metal-Assisted Chemical Etching (MACE) of silicon in HF-H 2 O 2 using silver nanoparticles as catalysts. Our aim is a better understanding of the process to elaborate new 3D submicrometric surface structures useful for light management. We investigated MACE over the whole range of silicon doping, i.e., p ++ , p + , p, p − , n, n + , and n ++. We discovered that, instead of the well-defined and straight mesopores obtained in p and n-type silicon, in p ++ and n ++ silicon MACE leads to the formation of cone-shaped macropores filled with porous silicon. We account for the transition between these two pore-formation regimes (straight and cone-shaped pores) by modeling (at equilibrium and under polarization) the Ag/Si/electrolyte (HF) system. The model simulates the system as two nanodiodes in series. We show that delocalized MACE is explained by a large tunnel current contribution for the p-Si/Ag and n-Si/HF diodes under reverse polarization, which increases with the doping level and when the size of the nanocontacts (Ag, HF) decreases. By analogy with the results obtained on heavily doped silicon, we finally present a method to form size-controlled cone-shaped macropores in p silicon with silver nanoparticles. This shape, instead of the usual straight mesopores, is obtained by applying an external anodic polarization during MACE. Two methods are shown to be effective for the control of the macropore cone angle: one by adjusting the potential applied during MACE, the other by changing the H 2 O 2 concentration. Under appropriate etching conditions, the obtained macropores exhibit optical properties (reflectivity ∼3 %) similar to that of black silicon

Versatile approach to nanoporous polymers with bicontinuous morphology using metal templated synthesis

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