Investigation of Co3Mo and Co6Mo7 Binary Alloys as Electrocatalysts for Hydrogen Evolution Reaction in Acidic Media

Metal alloys have become ubiquitous choice as catalysts for electrochemical hydrogen evolution in alkaline media. However, scarce and expensive Pt remains the key electrocatalyst in acidic electrolytes making the search for earth-abundant and cheaper alternatives appealing. Herein, we present a facile and efficient synthetic route towards polycrystalline Co₃Mo and Co₆Mo₇ metal alloys that achieve competitively low overpotentials of 115 mV and 160 mV at 10 mA cm^–2 in 0.5 M H₂SO₄. Both alloys outperform Co and Mo metals which showed significantly higher overpotentials and lower current densities when tested under identical conditions. However, the low overpotential in Co₃Mo comes at the price of stability. It rapidly becomes inactive when tested under applied potential bias. On the other hand, Co₇Mo₆ retains the current density over time without the evidence of current decay. The findings demonstrate that even in free-standing form and without nanostructuring polycrystalline bimetallic electrocatalysts could challenge the dominance of Pt in the acidic media if the ways for improving their stability were found.