Highly efficient and stable vanadium-based electrocatalysts: Stoichiometric iron vanadium sulfides for water-oxidation at large current densities

Abstract

Rational design of inexpensive electrocatalysts with high activity towards oxygen evolution reaction (OER) consisting of a complex four-electron process is of great importance for developing renewable energies in the form of hydrogen fuel from water electrolysis. Herein, we develop an exceptionally active and stable OER electrocatalyst, stoichiometric iron vanadium sulfide (Fe1.94V1.06S4) grown on nickel foam (NF). This electrocatalyst affords current densities of 100 and 1500 mA cm−2 at low overpotentials of 193 and 253 mV, respectively, and has stable operation time of exceeding 150 h in alkaline electrolyte, which dramatically outperforms most of the recently reported electrocatalysts (typically, the state-of-the-art NiFe-based electrocatalysts). Systematic investigations on the effects of vanadium and its valence state demonstrate that Fe3+ coupled with V2+ in Fe1.94V1.06S4 endows a larger benefit on the OER than the counterparts in FeV2S4 and vanadium-doped pyrrhotite (Fe7−xVxS8). Density functional theory (DFT) simulations reveal the highly conductive stoichiometric iron vanadium sulfides and favored binding energetics of the OER intermediates on them with a derived amorphous Fe–V oxyhydroxide overlayer due to the synergistically optimized the electronic structure. Thus, a novel bimetallic system containing low-valent vanadium is anticipated to work effectively to enable the communities to scrutinize and exploit new electrocatalysts for water splitting.