Novel Microporous Metal Phosphonates as Electrocatalyst for the Electrochemical Hydrogen Evolution Reaction

To regenerate the fuel cell energy resources and create an environmentally benign atmosphere, the conversion of water to hydrogen via the electrochemical hydrogen evolution reaction (HER) is one of the key reactions, and this has been gaining huge interest over the years. Thus, the design and synthesis of highly efficient electrocatalysts are crucial to address this matter by replacing the expensive state-of-the-art platinum-based catalysts. Herein, three novel microporous transition-metal-based phosphonate materials, that is, nickel phosphonate (NiDPA), nickel-cobalt phosphonate (NiCoDPA), and cobalt phosphonate (CoDPA), have been synthesized using a simple solvothermal reaction pathway without utilizing any templating agent. Among these, NiCoDPA exhibits high electrocatalytic activity toward HER due to its higher specific surface area with a regular microporous channel and synergistic effects of Ni and Co as compared with other as-synthesized catalysts. The presence of phosphorus atoms can increase the electron density at the bimetallic center, accelerating its electrocatalytic activity for HER with an overpotential of 112 mV and a Tafel slope of 78 mV dec-1 at a current density of 10 mA cm-2 in alkaline electrolytes. Notably, the NiCoDPA catalyst also displays outstanding stability up to 100 h without changing any significant potential. This research work focuses on the correlation between the structural and electrochemical properties in the energy conversion process.