Unveiling the synergistic effect of multi-valence Cu species to promote formaldehyde oxidation for anodic hydrogen production

Abstract

•Efficient anodic H2 generation is achieved on a Cu-based catalyst •FOR mechanism of Cu0–Cu+ synergy is clarified •Design guidelines for copper-based catalysts for FOR are proposed •A new strategy for the dual-sides H2 production electrolyzer is provided The ultra-low potential oxidation of aldehydes is a conspicuous replacement for oxygen evolution reaction due to its efficiency in lowering the energy required for hydrogen production and producing H2 on dual sides of the electrolyzer. However, the activity origin of catalysts and the reaction mechanism remains unclear. Herein, a formaldehyde oxidation reaction (FOR) with high current density (165 mA cm−2 at 0.35 VRHE) is realized on partially reduced CuO on Cu foam (Cux[email protected]) electrocatalysts. In situ characterizations and density functional theory calculations identified and investigated the existence of Cu0 and Cu+ and the synergistic effect for FOR and corroborate the reaction pathway. The results reveal that Cu0 can facilitate the reaction energy of HOCH2O∗ + HO∗, and Cu+ is more favorable for C–H bond cleavage. Meanwhile, H atoms in the produced H2 are verified to be entirely from HCHO. This work provides theoretical guidance for designing Cu-based electrocatalysts for FOR. The ultra-low potential oxidation of aldehydes is a conspicuous replacement for oxygen evolution reaction due to its efficiency in lowering the energy required for hydrogen production and producing H2 on dual sides of the electrolyzer. However, the activity origin of catalysts and the reaction mechanism remains unclear. Herein, a formaldehyde oxidation reaction (FOR) with high current density (165 mA cm−2 at 0.35 VRHE) is realized on partially reduced CuO on Cu foam (Cux[email protected]) electrocatalysts. In situ characterizations and density functional theory calculations identified and investigated the existence of Cu0 and Cu+ and the synergistic effect for FOR and corroborate the reaction pathway. The results reveal that Cu0 can facilitate the reaction energy of HOCH2O∗ + HO∗, and Cu+ is more favorable for C–H bond cleavage. Meanwhile, H atoms in the produced H2 are verified to be entirely from HCHO. This work provides theoretical guidance for designing Cu-based electrocatalysts for FOR.