Thermally reduced rGO‐wrapped CoP/Co2P hybrid microflower as an electrocatalyst for hydrogen evolution reaction

• Published in: Journal of the American Ceramic Society 2018-09, Vol.101 (9), p.3749-3754
• Main Authors: Kim, Taek‐Seung, Song, Hee Jo, Dar, Mushtaq Ahmad, Shim, Hyun‐Woo, Kim, Dong‐Wan
• Format: Article
• Language: English
• Subjects: catalysts/catalysis; Cobalt; cobalt/cobalt compounds; Electrocatalysts; Graphene; graphene oxide; hydrogen evolution reaction; Hydrogen evolution reactions; Hydroxides; Morphology; Noble metals; phosphates; Phosphides; Slope stability; Sulfuric acid; Synthesis; Thermal reduction
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.15581

Cobalt phosphides (CoPx) are potential candidates for use as high‐efficiency hydrogen evolution reaction electrocatalysts that can replace noble metals, such as Pt. Typically, CoPx can be synthesized by phosphidation with Co‐based precursors such as oxides or hydroxides. In this study, we propose a new strategy for synthesizing CoPx through the thermal reduction in cobalt phosphate (Co3(PO4)2). A reduced graphene oxide‐wrapped CoP/Co2P hybrid microflower was successfully synthesized by a facile coprecipitation method in a Co3(PO4)2 matrix, followed by a thermal reduction process. Co3(PO4)2 can be transformed to CoP/Co2P by treatment at 700°C for 1 hour, maintaining the original particle morphology with the assistance of reduced graphene oxide (rGO). In a 0.5 mol/L H2SO4 solution, the rGO‐CoP/Co2P microflower catalyzes the hydrogen evolution reaction with an overpotential of 156 mV at a current density of 10 mA cm−2, a Tafel slope of 53.8 mV dec−1, and good stability as observed through long‐term CV and chronoamperometry tests. We propose a new strategy for synthesizing CoPx through the thermal reduction of cobalt phosphate (Co3(PO4)2) for the high‐performance water‐splitting electrocatalyst.