Enhancement of hydrogen evolution activities of low-cost transition metal electrocatalysts in near-neutral strongly buffered aerobic media

•The advantages of HER in strongly buffered neutral pH are manifold.•Mo2C, MoS2, CoSe2 and NiSe2 were studied in phosphate buffered solution of pH 5.•An optimal buffer concentration of 1.75 M was consistently observed.•A reduction of about 100 mV in the onset overpotential could be achieved.•The electrocatalysts were oxygen tolerant with more than 90% HER selectivity.

The advantages of hydrogen evolution reaction (HER) in strongly buffered neutral pH are manifold including enhanced stability of the electrocatalysts, oxygen tolerance, safer and environmental friendly devices, etc., yet, not much research effort has been devoted on the subject. HER activities of several low-cost electrocatalysts like Mo2C, MoS2, CoSe2 and NiSe2 have been studied in sodium phosphate buffer solution of pH 5. An optimal buffer concentration of 1.75 M was observed for the electrocatalysts. Compared to un-buffered electrolyte, a reduction of about 100 mV in the onset overpotential has been achieved. The electrocatalysts are highly oxygen tolerant with more than 90% HER selectivities. Furthermore, electrochemical surface area of Mo2C was evaluated by capacitance and surface oxidation methods to obtain an insight on the specific adsorption of buffer electrolytes.

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