Interfacial electronic engineering at a Cu/Ni heterojunction electrode enables stable and efficient formaldehyde electro–oxidation for hydrogen production

The electrocatalytic formaldehyde oxidation reaction (FOR) offers a unique pathway for simultaneous hydrogen and formate generation at the anode, presenting an energy–efficient alternative to the oxygen evolution reaction for hydrogen production. However, the inherent activity and stability of Cu–based electrocatalysts for FOR are still not satisfactory for practical application, primarily due to the facile oxidation of active Cu 0 sites to inactive Cu + /Cu 2+ species during operation. Herein, we construct a Cu/Ni heterojunction electrode via facile electrodeposition. Experimental and spectroscopic characterizations confirm interfacial electron transfer from Ni to Cu, creating an electron–rich Cu surface that resists oxidative deactivation. This electronic modulation results in exceptional FOR performance, achieving 100 mA·cm –2 at 0.1 V vs. RHE and remarkable stability over 100 h. In situ measurements further reveal that the optimized electronic structure of the Cu/Ni heterojunction electrode enhances the adsorption and conversion of the key H 2 C(OH)O intermediate. A bipolar H 2 production device incorporating a Cu/Ni anode achieves 100 mA·cm –2 at a cell voltage of 0.14 V. This work demonstrates the promise of interfacial electronic engineering in developing efficient catalysts for energy–saving hydrogen production.