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

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.