Robust and promising hydrogen and oxygen evolution reactions by a nanostructured bifunctional FeCoPd alloy electrocatalyst

Abstract

Herein, we developed trimetallic FeCoPd polyhedral alloy nanoparticles (NPs) as a new highly efficient and promising bifunctional electrocatalyst for hydrogen and oxygen evolution reactions (HER and OER). The as-synthesized polyhedral NPs possess mainly octahedral and cuboctahedral particles with exposed highly active {100} and less active {111} facets. The partial atmospheric surface oxidation of FeCoPd NPs led to the formation of oxidized metal ion sites for the adsorption of *OH and *OOH reactive species, and the catalyst on a graphite sheet substrate in a 1.0 M KOH electrolyte can afford 10 mA cm⁻² current density at 197 mV overpotential in the OER. The surface metal sites of the catalyst act as the active site for the adsorption of H_ads reactive species for the HER, exhibiting a 52 mV overpotential at 10 mA cm⁻² in 0.5 M H₂SO₄. The FeCoPd electrocatalyst offered a high current density of 1000 and 550 mA cm⁻² in acidic (at −0.40 V, HER) and basic (0.540 V, OER) media, respectively. With a high mass activity of 4.67 A g⁻¹, it also showed long cycling stability over 10 000 cycles and durability for 100 h at high constant current density (100 mA cm⁻²) without any degradation of the catalyst. It also demonstrated OER stability in 30 wt% KOH with 180 mV overpotential at 10 mA cm⁻². Computational studies were further used to understand and validate a proposed mechanism corroborating the experimental results.