Highly Active and Durable NiMoMn Hydrogen Evolution Catalysts for Proton-Exchange Membrane Water Electrolysis

Proton-exchange membrane water electrolysis (PEMWE) powered by renewable energy sources is an eco-friendly technology for the mass production of hydrogen. One of the major obstacles in the commercialization of PEMWE is the necessity of using precious metal catalysts under corrosive operating conditions, which can be partially mitigated by using nonprecious metal catalysts for the cathode, where the conditions are less harsh than those for the anode. However, the use of nonprecious transition metal catalysts limits both performance and durability. To overcome this limitation, a wide range of NiMoMn ternary alloy catalyst compositions were fabricated by electrodeposition, and their performances were evaluated. The best-performing Ni_82.1Mo_11.6Mn_6.3 alloy catalyst exhibited an outstanding hydrogen evolution performance with an overpotential of 16 mV at −10 mA cm⁻², and with an increase of only 8 mV after 10,000 potential cycles for durability testing. The application of this material in a PEMWE single cell gave a favorable performance of 1.936 A cm⁻² at 2.0 V_cell, and an excellent degradation rate of 2.2 mV h⁻¹ in a durability test performed at 1 A cm⁻². This high performance and excellent durability of the Ni_82.1Mo_11.6Mn_6.3 catalyst was attributed to the modulation of its electronic structure, in addition to a large electrochemical surface area, and stable Mn oxide formation on the surface. These results indicate the potential of this catalyst for use in lowering the hydrogen production costs associated with PEMWE.