Tuning Electronic Structures of Transition Metal Carbides to Boost Oxygen Evolution Reactions in Acidic Medium.

Abstract

Developing low-cost, efficient, and robust nonprecious metal electrocatalysts for oxygen evolution reactions (OER) in acidic medium is the major challenge to realize the application of the proton exchange membrane water electrolyzer (PEM-WE). It is well-known that transition metal carbides (TMCs) have Pt-like electronic structures and catalytic behaviors. However, monometallic carbides in acidic medium show ignored OER activities. Herein, we reported that the catalytic activity of the TMCs can be enhanced by constructing bimetallic carbides (TiTaC2) fabricated through hydrothermal treatment followed by an annealing process, and further by doping fluorine (F) into the bimetallic carbides (TiTaFxC2). The as-prepared reduced graphene oxide (rGO) supported TiTaFxC2 nanoparticles (TiTaFxC2 NP/rGO) show state-of-the-art OER catalytic activity, which is even superior to Ir/C catalyst (an onset potential of only 1.42 V vs RHE and the overpotential of 490 mV to reach 100 mA cm-2), fast kinetics (Tafel slope of only 36 mV dec-1), and high durability (maintaining the current density at 1.60 V vs RHE for 40 h). Detailed structural characterizations together with density functional theory (DFT) calculations reveal that the electronic structures of the bimetallic carbides have been tuned, and their possible mechanism is also discussed.