Facile Synthesis of Nanoporous Transition Metal-Based Phosphates for Oxygen Evolution Reaction

Abstract

Due to unique structural porosity, low-cost, and good catalytic activity, oxygen evolution reactions over 3d transition elements have gained immense attention in recent years. Herein, we report the fabrication of three different metal phosphates, e. g. Co-phosphate (CoPO), Ni-phosphate (NiPO), and Ni−Co-phosphate (NiCoPO) using the corresponding metal sources and phosphoric acid as a phosphorus source under hydrothermal conditions without using any structure-directing agent. Since the as-prepared metal-based phosphates exhibit high surface area with good interparticle porosity and contain transition metals in the material frameworks, these materials have been investigated for electrocatalytic oxygen evolution reaction (OER). Among the three metal phosphates, the as-synthesized CoPO catalyst shows efficient electrocatalytic activity toward OER, with an overpotential of 350 mV at 10 mA cm−2 in 1.0 M KOH solution and a relatively low Tafel slope of 60.7 mV dec−1. The good electrocatalytic performance of CoPO is attributed to its higher specific surface area and pore volume compared to other two catalysts. The CoPO-modified electrode also shows a high stability up to 15 h at a constant potential of 1.58 V, suggesting its promising future for OER catalysis.