Au-nanoparticles-decorated CeO2 electrocatalyst synthesized by direct growth and wet impregnation for enhanced oxygen evolution reaction

Abstract

Water splitting is a promising method for producing pure hydrogen and oxygen electrochemically. However, the sluggish kinetics of the oxygen evolution reaction (OER) at the anode of a water splitting system reduces the efficiency of the reaction. To address this issue, various electrocatalysts have been developed for use in the OER. Among them, transition-metal-based materials (TMBMs) have emerged as promising candidates owing to their abundance, low cost, high redox states, and synergistic effects. The catalytic performance of TMBMs can be further enhanced by incorporating small amounts of noble metals. Based on this underlying principle, we developed trace amounts of gold nanoparticles (AuNPs)-decorated cerium oxide (CeO2) nanostructured electrocatalyst for a highly efficient OER. Previously, these composite materials have been utilized for this purpose; however, our approach is simple and facile: we incorporate noble metal elements on nanostructured catalysts synthesized by hydrothermal synthesis or electrodeposition. Metal salt aqueous solution-based alkali-free two different routes (hydrothermal synthesis or electrodeposition) were used for the direct growth of nanostructured CeO2 on nickel foam, followed by surface modification via the incorporation of gold using a simple wet impregnation method. The hydrothermally synthesized CeO2 electrode showed higher OER performance than the electrodeposited CeO2 electrodes. In both CeO2 nanostructures, AuNPs-decorated on the surfaces exhibited improved OER performance. Among the electrodes synthesized in this work, the hydrothermally synthesized AuNPs-decorated CeO2 nanostructures (termed HCA herein) exhibited a low overpotential 0.31 V at a current density of 10 mA cm−2, a low Tafel slope (30.25 mV dec−1), and a performance retention of 97% after 50 h, indicating excellent and stable OER performance. Hence, this approach for the synthesis of nanostructured composites can be used to produce other effective electrocatalysts for OER applications.