(345c) Electrocatalytic Oxidative Dehydrogenation of Biorenewable Aldehydes over Cu-Based Catalysts for Bipolar Hydrogen Production

Water electrolysis has been considered a green process for hydrogen production. Conventional electrolysis is limited by the sluggish anodic oxygen evolution reaction (OER), leading to high energy input. In addition, the temporal spatial coupling of the production of H₂ and O₂ can cause issues associated with safety, economic feasibility, and system flexibility. Herein, we reported our work on replacing OER with an electrocatalytic oxidative dehydrogenation (EOD) of biorenewable aldehydes for bipolar H₂ production at low cell voltages and high current densities. Experimental and DFT studies suggested a reasonable barrier for C-H dissociation on Cu surface, mainly through the diol intermediate, with the potential-dependent competition with Cannizzaro reaction. We revealed that EOD on metallic Cu surface was linked to an autocatalytic Cu oxides reduction by aldehydes along with H₂ evolution. The EOD kinetics and durability was further enhanced by a porous CuAg catalyst prepared by a galvanic replacement method. We engineered a bipolar H₂ production system using membrane-electrode assembly-based flow cells to facilitate mass transport, achieving a combined faradaic efficiency (FE) of ~200% to H₂ and the maximum H₂ partial current density of 248 and 390 mA/cm² at cell voltages of 0.4 V and 0.6 V, respectively. We further studied other CuM (M= Pt, Pd, Au) bimetallic catalysts for EOD reaction, and found that dispersing Pt into Cu (CuPt) exhibited a unique synergistic effect for furfural EOD possibly via efficient C-H cleavage on Cu and favorable furfural binding on Pt. The CuPt anode-based flow electrolyzer has achieved a higher current density of 498 mA/cm² at a low cell voltage of 0.6 V and FE of >80% to H₂. Inexpensive dialysis membranes and non-noble metal HER catalysts are possibly used for bipolar H₂ production, which provides an alternative approach for distributed manufacturing of green hydrogen and carbon chemicals in the future.