Formaldehyde oxidation boosts ultra-low cell voltage industrial current density water electrolysis for dual hydrogen production

The high cost is a major issue that has contributed to the slow industrialization of electrolytic water. To reduce the cell voltage to below 0.5 V, we constructed a hybrid electrolytic water system with coupled hydrogen evolution reaction (HER) and formaldehyde oxidation reaction (FOR). For FOR, the abundant Cu0 and Cu+ in nitrogen-doped Cu/Cu2+1O on Cu foam (N-Cu/Cu2+1O/CF) can effectively promote the adsorption and activation of H2O and HCHO molecules, and facilitate the cleavage of O-H and C-H, while nitrogen doping can promote the exposure of Cu active sites. For HER//FOR, a cell voltage of only 0.42 V is required to achieve 500 mA cm−2. The system can not only produce H2 routinely at the cathode through HER but also release H2 by HCHO oxidation. The construction of a dual hydrogen production system with industrial current density at ultra-low voltage provides a new idea to reduce the cost of hydrogen production.