Synergistic effect of Pt-loaded Co N C electrocatalysts for hydrogen evolution reaction in alkaline conditions

• Pt NPs dispersed on Co-N-C support exhibits synergistically enhanced H 2 production in alkaline media. • Co-N-C facilitates water-dissociation step to improve HER on Pt active sites of Pt/Co-N-C. • High performing Pt/Co-N-C has larger charge ratio of H upd /OH ad on Pt compared to Pt/C. Designing efficient electrocatalysts for the hydrogen evolution reaction (HER) is important for a renewable and sustainable hydrogen economy. Alkaline HER remains particularly challenging because it involves water dissociation in addition to hydrogen recombination. Herein, we developed a simple precursor solution-based electrocatalyst in which Pt nanoparticles (NPs) are positioned independently of the Co-dispersed nitrogen-doped carbon (Co-N-C). The Pt/Co-N-C catalyst exhibited enhanced HER activity in an alkaline electrolyte compared to Pt/C and Co-N-C, achieving a decreased overpotential (33 mV at 10 mA cm −2 ) and lower Tafel slope (36.8 mV dec −1 ). Comparison of HER activities under acidic and alkaline electrolyte conditions revealed that the synergistic enhancement of Pt/Co-N-C was only obtained under the alkaline condition. Evaluation of the adsorption/desorption of H or OH through cyclic voltammetry analysis suggested that Co-N-C support can play a role to facilitate water-dissociation under alkaline conditions and leads to a larger charge ratio of H upd /OH ad on Pt, thus improving the HER activity at the Pt NP active sites.