Cu nanowire arrays on electroless deposited cu foam for efficient electrocatalytic formaldehyde selective conversion to co-produce H2 and valuable chemicals

Hydrogen (H 2 ) is a promising green alternative fuel; however, the widespread adoption of H 2 production technologies is limited by high energy consumption and significant carbon emissions. Here, we have developed a bipolar H 2 production electrolyzer that purifies wastewater and produces H 2 with ultra-low energy consumption by combining the formaldehyde 1-electron oxidation reaction (FOR-1) at the anode and the hydrogen evolution reaction (HER) at the cathode. The electroless Cu electrode exhibits high selectivity and activity for the 1-electron pathway of formaldehyde oxidation (i.e., FOR-1), enabling the anodic conversion of formaldehyde into valuable H 2 and formate. This facilitates the treatment of toxic formaldehyde waste while doubling H 2 production efficiency of the electrolyzer. Unlike conventional water electrolysis, the formaldehyde-water electrolyzer demonstrates a cell voltage reduction of 1.49 V at 10 mA/cm 2 . At 100 mA/cm 2 , the energy consumption is reduced to only 25 % of that in conventional systems, even with the use of a nickel foam cathode. Moreover, formaldehyde in wastewater is fully degraded within 50 min, highlighting its practical application potential.