Unlocking Dual‐Pathway Low‐Potential Aldehyde Oxidation on Chromium‐Doped Copper Catalysts

The low-potential aldehyde oxidation reaction (LPAOR) is emerging as a pivotal anodic strategy in hybrid water electrolysis and biomass fuel cell systems, enabling low-energy hydrogen production and biomass upgrading. However, the most prior research focus on the stability of monometallic Cu catalysts and the structural modulation to accelerate hydrogen coupling, without elucidating the entire reaction pathways. Herein, a Cr-doped mixed-valent Cu nanowire arrays (An-CrCu_xO-AC NWAs) catalyst is prepared to elucidate the dual pathways in LPAOR. Owing to the regulation of Cr on the adsorption ability of OH*, the active H* generated by C─H bond cleavage of aldehyde group combines with OH* forming H₂O via Volmer step, triggering parallel one-electron and two-electron reaction pathways for An-CrCu_xO-AC NWAs catalyst. Furthermore, Cr incorporation tunes the electronic structure of Cu, modulating the adsorption capacity of substrates and kinetics energy barrier of key elementary step, which makes an enhanced LPAOR performance. Concretely, the An-CrCu_xO-AC NWAs catalyst attains a current density of 100 mA cm^-2 at 0.224 V_RHE, remarkably surpassing An-Cu_xO-AC NWAs catalyst (0.271 V_RHE). A hybrid system coupled LPAOR with oxygen reduction reaction realizes a peak power density of 43.0 mW cm^-2 at 103.1 mA cm^-2 using An-CrCu_xO-AC NWAs as anodic catalyst.