Amorphous Ni(OH)2 Coated Cu Dendrites with Superaerophobic Interface for Bipolar Hydrogen Production Assisted with Formaldehyde Oxidation.

Since formaldehyde oxidation reaction (FOR) can release H2, it is attractive to construct a bipolar hydrogen production system consisting of FOR and hydrogen evolution reaction (HER). Although copper-based catalysts have attracted much attention due to their low cost and high FOR activity, the performance enhancement mechanism lacks in-depth investigation. Here, an amorphous-crystalline catalyst of amorphous nickel hydroxide-coated copper dendrites on copper foam (Cu@Ni(OH)2/CF) is prepared. The modification of Ni(OH)2 resulted in hydrophilic and aerophobic states on the Cu@Ni(OH)2/CF surface, facilitating the transport of liquid-phase species on the electrode surface and accelerating the release of H2. The Open circuit potential (OCP) and density functional theory (DFT) calculations indicate that this core-shell structure facilitates the adsorption of HCHO and OH-. In addition, the catalytic mechanism and reaction pathway of FOR are investigated through in situ FTIR and DFT calculations, and the results showed that the modification of Ni(OH)2 lowered the energy barrier for C─H bond breaking and H─H bond formation. In the HER//FOR system, Pt/C//Cu@Ni(OH)2/CF can provide a current density of 0.5 A cm-2 at 0.36 V and achieve efficient and stable H2 production. This work offers new ideas for designing electrocatalysts for bipolar hydrogen production system assisted with formaldehyde oxidation.