Modulation of electronic structure of nickel selenide via iron doping for energy-saving hydrogen production coupled with sulfion upgrading

Abstract

Hybrid water electrolysis is a promising approach to achieve energy-saving hydrogen (H2) generation by replacing oxygen evolution reaction with thermodynamically advantageous sulfion oxidation reaction (SOR). Herein, we design iron-modified nickel selenide nanosheet arrays (Fe-Ni0.85Se) as a bifunctional hydrogen evolution reaction (HER) and SOR electrocatalyst to simultaneous facilitate H2 production and convert sulfion into valuable sulfur product. The Fe-Ni0.85Se needs low overpotential of 114 mV for HER and working potential of 0.340 V for anodic SOR to attain 10 mA cm−2. Moreover, the two-electrode hybrid electrolysis cell employing Fe-Ni0.85Se as cathode and anode requires small voltage of 0.439 V at 10 mA cm-2, which greatly reduces operation voltage by 1.186 V compared with overall water splitting, realizing energy-saving H2 production and high value-added sulfur source. The theoretical calculations verify that the Fe modification can accelerate water dissociation, optimize the adsorption behavior of hydrogen adsorption and sulfion, and promote conversion process of sulfur intermediates. This work offers a simple approach to develop bifunctional catalytic electrodes for economically viable H2 generation and sulfur recovery.