Molybdenum Single-Atom Solid-Acid Catalyst for the Hydrogen Evolution Reaction in the Alkaline Electrolyte

Tailoring the gradient-pH catalytic environment around single-atom centers is rather meaningful in water electrolysis. Herein, we report a two-step strategy including hydrothermal and electrochemical optimization to synthesize PO₄^3– and AlO_x^– simultaneously coordinated Mo single-atom catalysts on carbon-coated Ni foam. The abundant bridging oxygen atoms between Mo and P/Al atoms result in appealing adsorption and activation of water reactant, as well as an energy-favorable hydrogen desorption behavior due to their solid-acid nature. Consequently, the well-designed Mo–P–Al@NF @NF single-atom solid-acid catalyst system exhibits a comparable hydrogen evolution reaction activity in 1.0 M KOH electrolyte with current response beginning at nearly zero overpotential, delivering a typical current density of 10 mA/cm² only requiring overpotential of 48 mV. Moreover, it also shows comparable stability with negligible activity degradation after continuous hydrogen production over 100 h. Our work may provide a guideline for the development of single-atom solid-acid catalysts toward highly efficient water electrolysis and beyond.