Mixed NiCo-phosphate/sulphide heterostructure as an efficient electrocatalyst for hydrogen evolution reaction

In this work, we report an unexplored heterostructured catalyst consisting of Ni-Co-phosphate/sulphide phases (NCPSP) on carbon fibre paper through a single-step gas-solid reaction route for hydrogen evolution reaction (HER) in an acidic medium. The heterostructured electrode film of NCPSP depicted considerably enhanced electrochemical HER performance compared to the heterostructured controlled catalyst films consisting of Ni-Co-phosphide phases (NCPP), Ni-Co-sulphide phases (NCSP), and Ni-Co-phosphate/phosphide phases (NCPPP). Electrochemical and structural characterization reveals that superior catalytic credentials of NCPSP can be attributed to kinetically favourable H binding on the sulphur sites of transition metal (TM) sulphides and their beneficial heterostructure with TM phosphate component. Specifically, the minimum overpotential of 53 mV and 97 mV is observed for cathodic HER current of 10 mA cm(-2) and 100 mA cm(-2), respectively. The low Tafel slope of 43 mV dec(-1) reveals the favourable Volmer-Heyrovsky mechanism. Also, superior kinetics was revealed by the low charge transfer resistance of 28 Omega. The catalytic credentials of NCPSP are also well in alignment with the highest values reported for the best state of art catalysts.