Integrating electrocatalytic seawater splitting and biomass upgrading via bifunctional nickel cobalt phosphide nanorods

Abstract

The high overpotential of the oxygen evolution reaction (OER) and the undesirable chlorine evolution reaction (ClER) severely limit the hydrogen production efficiency of seawater electrolysis. The organic electrooxidation reactions, involving C–H bond oxidation with low bond dissociation energy in the rate-limiting step, can possess lower oxidation potential than the OER as well as prevent the ClER. Herein, we demonstrate a strategy for replacing the sluggish OER by thermodynamically favorable biomass oxidation for scaling up the electrolysis of alkaline seawater. A xylose electrooxidation reaction (XOR) holds great promise for superseding the OER in seawater electrolysis, which not only simultaneously produces valuable formic acid and hydrogen, but also improves energy utilization. By utilizing NiCoP metal phosphide as the bifunctional electrode, the XOR shows an apparent overpotential reduction of 290 mV at 100 mA cm⁻² as compared with the OER in the alkaline seawater electrolyte. Furthermore, the xylose-assisted seawater electrolysis exhibits a high formic acid selectivity of at least 94.6% and a high hydrogen production rate of 150 mL cm⁻². This work provides a universal and an effective pathway for hydrogen production from seawater and biomass upgrading.