Durability of nanostructured non-precious MoS2-based electrocatalysts for H2 evolution in PEM water electrolysis

An assessment of the durability characteristics of nanostructured MoS2-carbon black composite electrocatalysts for hydrogen evolution was carried out in an electrolysis single cell. The cathodic electrocatalyst was combined to a standard Nafion (R) membrane and an IrO2 anode to form a membrane-electrode assembly. Different MoS2 electrocatalysts were developed. These were benchmarked over a commercial MoS2 catalyst and a state-of-the-art Pt/C cathode. The addition of high surface area Ketjenblack EC-600JD (R) carbon during the hydrothermal preparation resulted in a suitable interaction between the formed nanostructured MoS2 (crystallite size: 4 nm) and the carbon black. This allowed to improve electronic percolation also reducing mass transport constraints and resulted in a significantly better efficiency (cell voltage <1.8 V at 1 A cm(-2)) compared to the other MoS2 catalyst formulations. The most promising MoS2 catalyst-based MEA achieved a voltage efficiency for water splitting >82 % during a 1350-h durability test with continuous improvement of performance versus time. Formation of a sub-stoichiometric MoS2-x phase was observed. The end-of-test performance exceeded 3.1 A cm(-2) at a cell voltage of 2 V. Such performance was relatively lower than that of a state-of-the-art Pt/C catalyst but promising for the application of non-precious group metal cathodes in PEM electrolysis.