Cobalt oxide/cerium oxide heterogeneous interfaces as advanced durable and bifunctional electrocatalysts for robust industrially relevant overall water splitting

Abstract

The development of carbon-dioxide-free energy technology using renewable resources has become more urgent due to the continuously increasing global demand for energy. Electrochemical water splitting is a convenient way to produce clean hydrogen fuel. In the present study, we present electrodeposited non-precious mixed-phase Co oxide and Ce oxide heterostructured electrodes as bifunctional electrocatalysts for both oxygen and hydrogen evolution reactions in an alkaline medium. To achieve this, we fabricated various Co_1−xCe_x films (where x = 0.15 and 0.50) by varying the Co/Ce molar ratios of 0.85 : 0.15 and 0.50 : 0.50. The optimized material, referred to as Co_0.85Ce_0.15, exhibits an ultralow overpotential of 177 mV and 76 mV for the OER and HER, at 20 and −10 mA cm⁻², respectively. The overall water splitting (OWS) electrolyzer constructed with optimized electrodes exhibits ultralow cell voltages of 1.56, 2.05, and 2.27 V to achieve current densities of 10, 500, and 1000 mA cm⁻² with superbly enhanced electrochemical durability over 40 h at industrially relevant high biases of up to 1000 mA cm⁻². Moreover, the OWS further reduced the cell voltage to 1.48 V at an operating temperature of 55 °C, whereas the industrially relevant current density of 1000 mA cm⁻² was easily achieved at a cell voltage of only 2.07 V. This work provides new insights for the optimization of multi-metal LDHs by engineering intermediate energy barriers for bifunctional catalysts.