Composition Tuning of Ultrafine Cobalt-Based Spinel Nanoparticles for Efficient Oxygen Evolution
Jingbo Han, Xiaohe Liu, Hao Wan, Dan Wu, Gen Chen, Junhui Li, Yijun Cao, Renzhi Ma
Abstract
The kinetically sluggish oxygen evolution reaction has been considered as the bottleneck of energetic overall water splitting for hydrogen generation. Herein, a series of binary CoV and ternary CoFeV spinel catalysts were synthesized via a solvothermal process. The particle size gradually decreased followed by the increase in metal species. As the result of ultrafine size (∼4 nm) and composition optimization, CoFeV spinel nanoparticles with Co:Fe:V molar ratio of 1.8:1.1:1 showed a higher performance than other congeneric Co-based spinels and benchmark RuO2 electrocatalyst in electrocatalytic oxygen evolution. The needed overpotential to reach 10 mA cm–2 is only 248 mV with a lower Tafel slope of 52.8 mV dec–1 and an excellent durability of over 18 h. The high activity of ternary CoFeV spinel nanoparticles was further made evident through a solar-to-hydrogen system for the overall water splitting, achieving the current density as 224 mA cm–2 at 2.5 V with a high Faradaic efficiency of 97.7% for the hydrogen product. This work further heralds a great potential of developing nanostructures with carefully designed composition for electrochemistry-related applications.