Nanosized CoWO 4 and NiWO 4 as efficient oxygen-evolving electrocatalysts

A main challenge to improve the performance of large scale energy technologies based on photo-driven or electricity-driven production of hydrogen from water is the development of efficient and economical water oxidation catalysts. Herein, we, for the first time, report the CoWO4 and NiWO4 nanoparticles as new highly efficient electrode materials for oxygen evolution reaction (OER) in alkaline solutions. The study has shown that both the electrocatalysts efficiently evolve oxygen. At an overpotential (η) in the OER region, the oxygen evolution current density on CoWO4 was much higher than that on NiWO4. At the current density of 10 mA cm−2 (per geometrical area) in 1 M KOH, catalytic films of CoWO4 and NiWO4 on GC substrate produced η ≈ 388 and 507 mV, respectively. When the GC catalyst support was replaced by nickel one, the overpotential required to achieve the current density of 10 mA cm−2 on CoWO4 (η ≈336 mV) and NiWO4 (η ≈ 363 mV) electrodes decreased significantly. The OER has a low Tafel slope (≈2 × 2.3 RT/3F) on both catalysts and follows nearly second order kinetics with respect to OH− concentration, regardless of the nature of the support material. The catalytic films on Ni exhibited outstanding stability.