Self-supported amorphous phosphide catalytic electrodes for electrochemical hydrogen production coupling with methanol upgrading

Abstract

Efficient catalytic electrodes for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) are pivotal for massive production of green hydrogen from water electrolysis, and the further replacement of kinetically sluggish OER by tailored elecrooxidation of certain organics is a promising way to co-produce hydrogen and value-added chemicals via a more energy-saving and safer manner. Herein, amorphous Ni-Co-Fe ternary phosphides (NixCoyFez-Ps) with different Ni:Co:Fe ratios electrodeposited onto Ni foam (NF) substrate were served as self-supported catalytic electrodes for alkaline HER and OER. The Ni4Co4Fe1-P electrode deposited in solution at Ni:Co:Fe ratio of 4:4:1 displayed low overpotential (61 mV at −20 mA cm−2) and acceptable durability for HER, while the Ni2Co2Fe1-P electrode fabricated in deposition solution at Ni:Co:Fe ratio of 2:2:1 showed good OER efficiency (overpotential of 275 mV at 20 mA cm−2) and robust durability, the further replacement of OER by anodic methanol oxidation reaction (MOR) enabled selective production of formate with 110 mV lower anodic potential at 20 mA cm−2. The HER-MOR co-electrolysis system based on Ni4Co4Fe1-P cathode and Ni2Co2Fe1-P anode could save 1.4 kWh of electric energy per cubic meter of H2 relative to mere water electrolysis. The current work offers a feasible approach to co-produce H2 and value-upgraded formate via an energy-saving manner by rational design of catalytic electrodes and construction of co-electrolysis system, and paves the way for cost-effective co-preparation of more value-added organics and green hydrogen via electrolysis.