Template‐Free Synthesis of Zinc Cobalt Oxides/Phosphides (Co₂P/CoO/ZnCo₂O₄) Hollow Sub‐Micron Boxes as Hydrogen Evolution Reaction Catalysts

Abstract

In this work, we report the template‐free synthesis of zinc cobalt oxides/phosphides (Co2P/CoO/ZnCo2O4) hollow sub‐micron boxes as electrocatalysts for HER (hydrogen evolution reaction). The synthesis of such sub‐micron box starts with the preparation of the hollow oxide sub‐micron box and is followed by a phosphorization process. It is proven that the selective etching induces by cation exchange (Zn2+ and Co2+) was the key to the formation of the hollow structure. The analysis of chemical states and electrochemical activity further reveals Zn enhanced the intrinsic activity of catalysts by increasing the electron density of Co in final products. The optimized ZnCo‐OP hollow sub‐micron box exhibits good HER activity with overpotentials of 112 mV at 10 mA/cm2 and 197 mV at 250 mA/cm2.

Recent progress in ZnCo2O4 and its composites for energy storage and conversion: a review

“…Among those works, we can highlight that reported by Zhang and colleagues 289 where zinc cobalt oxides/phosphides (Co2P/CoO/ZnCo2O4) hollow submicron was obtained…”

“…The main reason for this is that the production of high-purity hydrogen from the water-splitting method 293 still is restricted by the sluggish kinetics of the OER. 264 Among these works, we can highlight that reported by Zhang and colleagues 283 where zinc cobalt oxide/phosphide (Co 2 P/ CoO/ZnCo 2 O 4 ) hollow submicron boxes were obtained and used as an electrode material for the HER. The electrocatalyst showed an overpotential of 112 mV at À10 mA cm À2 current density; for comparison purposes the commercial Pt/C electrode also was tested and presented an overpotential of 19 mV at the same current density.…”