Synthesis of polymetallic oxide nanoarrays as efficient hydrogen evolution reaction electrocatalyst for alkaline seawater and urea splitting

Abstract

Nowadays, with the depletion of traditional fossil resources, hydrogen energy comes into our eyes as a renewable and sustainable energy source. Electrocatalytic water splitting has been widely studied as an environmentally friendly method to produce hydrogen rapidly and large-scale. Since 96.5 % of the world’s abundant water resources are seawater, exploring an economical and efficient catalyst for seawater splitting is an attractive method to realize industrial hydrogen production. In this paper, polymetallic oxide Mn-MoWNi catalyst was in situ synthesized on nickel foam using one-step hydrothermal approach and composite strategy. The catalyst has excellent hydrogen evolution reaction (HER) performance in seawater and urea solution containing 1 M KOH. In 1 M KOH alkaline seawater solution, Mn-MoWNi only requires overpotential of 261 mV to drive the current density of 100 mA cm−2. When the current density of 100 mA cm−2 was reached in the alkaline solution of 1 M KOH + 0.5 M Urea, the overpotential of Mn-MoWNi catalyst was only 206 mV. After 15 h stability measurement in 1 M KOH alkaline seawater solution, the surface morphology of Mn-MoWNi was changed and corroded, indicating that its stability needs to be improved. Density functional theory calculations show that in Mn-MoWNi catalysts, MoO3 promotes the hydrogen adsorption ability of the material, while MnO2 promotes the electrical conductivity of the electrode, and both of them work synergistically with WO3 and NiWO4 to jointly improve the activity of the catalyst.