Effect of phosphorus on controlling and enhancing electrocatalytic performance of Ni-P-TiO2-MnO2 coatings

Electroless Ni-P coatings have received profound interests in recent years for electrocatalytic Hydrogen Evolution Reaction (HER). Their performance can be significantly enhanced by incorporating metal oxides and tuning the electrochemical and surface characteristics by varying the coating composition. The present work focused on the preparation of Ni-P-TiO2-MnO2 coatings by an electroless method, for catalytic alkaline HER. At first TiO2-MnO2 mixture oxide was prepared and its crystalline phase, elemental, bonding and morphological characteristics were analyzed by XRD, XPS, FT-IR and TEM. The TiO2-MnO2 mixture oxide incorporated Ni-P coatings were developed and their electrocatalytic activity was tuned by varying composition. The electrode with 11.32 at.% phosphorus and 14.42 at.% oxygen on the surface exhibited very high catalytic activity. The optimized Ni-P-TiO2-MnO2 electrode had significantly high activity and accomplished hydrogen evolution at high current densities (250 mA/cm2) with low overpotential (−142 mV) and low Tafel slope. The electrode had high double layer capacitance (1.29 × 10−3 F). The proposed mechanism of HER on the Ni-P-TiO2-MnO2 electrode composed of Volmer hydrogen adsorption facilitated by Ni metal in the coating and H2 evolution via Heyrovsky reaction.