CoS2-TiO2 hybrid nanostructures: efficient and durable bifunctional electrocatalysts for alkaline electrolyte membrane water electrolyzers

Abstract

The development of efficient catalysts to overcome the significant overpotential of the oxygen evolution reaction (OER) is the key bottleneck in the large-scale production of pure hydrogen. In the present work, we describe a simple approach for the fabrication of CoS2-TiO2 hybrid catalysts by the heat treatment of a cobalt thiourea complex in the presence of TiO2. We show the CoS2-TiO2 hybrid as a bi-functional electrocatalyst for overall water splitting in alkaline electrolyte membrane water electrolyzers. The optimal CoS2-TiO2 hybrid offered low overpotentials of 231 and 198 mV for the OER and HER, respectively. Fundamental studies pertaining to the role of TiO2 in enhancing the catalytic activity of the materials using optical and electrochemical band gap measurements of the CoS2-TiO2 hybrids were carried out. Additionally, the constructed MEA using the CoS2-TiO2 hybrid showed higher performance with an approximately 234 mA cm-2 current density at a cell voltage of 1.9 V and exhibited extended durable operation over 200 h, as compared to the MEA constructed with state-of-the-art all-noble-metal electrodes. © 2018 The Royal Society of Chemistry.