Enhanced Bifunctional Catalytic Activity of Cobalt Phosphide Flowers Anchored N‐Doped Reduced Graphene Oxide for Hydrogen and Oxygen Evolution

Abstract

In this work, we demonstrate morphology‐controlled synthesis of flower‐like cobalt phosphide decorated on nitrogen doped reduced graphene oxide (NrGO), which act as bifunctional electrocatalysts toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The as‐synthesized CoP‐NrGO, formed via hydrothermal reaction followed by gas‐solid reaction, attains an OER current density of 10 mA cm−2 at an overpotential of 0.38 V, which is on par with that of its Co(OH)2‐NrGO counterpart and the benchmarked IrO2 catalyst. On the other hand, the conversion of Co(OH)2 to CoP is seen to improve its HER performance drastically. CoP‐NrGO reached a current density of 10 mA cm−2 at an overpotential of 0.184 V which is 0.204 V anodic to Co(OH)2‐NrGO. The improved performance could be attributed to reduced charge transfer resistance following the phosphidation process. From the comparison of the electrocatalytic performance of the catalysts, it can be inferred that phosphidation has a considerable effect only on the cathodic HER.

Vanadium-Doped Nickel Cobalt Layered Double Hydroxide: A High-Performance Oxygen Evolution Reaction Electrocatalyst in Alkaline Medium

“…In this regard, various derivatives of transition metals like oxide, hydroxide, chalcogenide, pictinides, etc. have been proven to serve as a highly efficient water oxidation catalyst. ,− Recently, among all types of catalysts, catalysts comprising hydroxide ions, specially layer double hydroxides (LDHs) with unique layered structures, have gained an important consideration for OER under alkaline conditions …”

Graphene-based materials as electrocatalysts for the oxygen evolution reaction: a review

“…Vineesh et al constructed cobalt phosphide flower-anchored N-doped reduced graphene oxide (CoP-NrGO) via the hydrothermal process and gas–solid reaction. 74…”

Three-dimensional reduced graphene oxide decorated with cobalt metaphosphate as high cost-efficiency electrocatalysts for the hydrogen evolution reaction

“…Cobalt-based phosphide in HER has a great deal of attention, in which HER properties of cobalt phosphide have been extensively studied. 5,10,20–23 These cobalt phosphide compounds due to their poor electrical conductivity can only achieve a good result for HER in specific electrolyte, but they can't reach a satisfactory level. At the same time, cobalt metaphosphate-based materials (including cobalt metaphosphate and cobalt sodium metaphosphate) have been widely used in energy-related fields such as batteries due to their cheapness, cleanliness, ease of preparation, and favorable physical and chemical properties.…”