Nanoconfined Se Anions in 2D CoP/Co2P as High-Performance Bifunctional Electrocatalysts for Efficient H2 Production with Urea-Assisted Alkaline Seawater Electrolysis

Abstract

Hydrogen production from seawater electrolysis is promising; however, seawater electrolysis is facing significant challenges due to sluggish oxygen evolution reaction (OER), corrosion in catalysts, chlorine evolution reaction, and precipitate formation over catalysts. Development of efficient electrocatalysts with high chemical stability during seawater electrolysis is of paramount importance. Nanoconfinement of anions in metal phosphides can optimize the electronic structure and modulate the electrocatalysts to favor seawater splitting. Herein, a strategic design employing uniform distribution of Se atoms over two-dimensional mixed-phase cobalt phosphide nanosheet arrays (2D CoP/Co2P) showed a stable and efficient bifunctional catalytic activity toward urea-assisted seawater splitting. A distinct Se-doped cobalt phosphide nanosheet array (Se0.1-CoP) grown over nickel foam (Se0.1-CoP/NF) reaches 100 mA cm–2 at 272 mV and 450 mV for hydrogen and oxygen evolution reactions, respectively, in alkaline media, which is considerably enhanced in comparison to undoped counterparts. Again, the bifunctional Se0.1-CoP/NF (±) cell shows remarkable performance and durability in a seawater-based electrolysis cell. The cell Se0.1-CoP/NF (+)||Pt/C(−) in urea-assisted alkaline seawater electrolysis required just 1.48 V to reach 100 mA cm–2, which is significantly lower than 1.79 V for an alkaline seawater cell with superior durability when tested for 100 h at 100 mA cm–2 current density.