Nanostructured Co2P Electrocatalyst forthe Hydrogen Evolution Reaction and Direct Comparison with MorphologicallyEquivalent CoP.

Metal phosphides have emerged aspromising Earth-abundant alternativesto platinum for catalyzing the hydrogen evolution reaction (HER) inacidic aqueous solutions. Here, Co2P nanoparticles havinga hollow, multifaceted, crystalline morphology have been evaluatedas HER electrocatalysts at a mass loading of 1 mg cm–2on Ti foil substrates. The Co2P/Ti electrodes requiredlow overpotentials of −95 and −109 mV to produce operationallyrelevant cathodic current densities of −10 and −20 mAcm–2, respectively. These values establish Co2P nanoparticles as highly active Earth-abundant HER catalystmaterials. Importantly, the Co2P nanoparticles are morphologicallyequivalent to previously reported CoP nanoparticle HER catalysts,allowing a direct side-by-side evaluation of their HER activities.Such comparisons of different metal phosphide HER catalysts with thesame constituent elements and morphologies are important for identifyingthe key materials characteristics that lead to high activity. [ABSTRACT FROM AUTHOR]