Porous Ni(OH)2 permselective membrane to identify the mechanism of hydrogen evolution reaction in buffered solution.

• Porous Ni(OH) 2 membrane resists phosphate but transfers OH− and H 2 • Phosphate ions directly participate in HER as reactant on Pt and Ni electrode • Phosphate ions enhance HER activity of Pt but lower HER activity for Ni electrode Phosphate buffer solution (PBS) is widely used in hydrogen evolution reaction (HER), however, the HER mechanism in PBS is still unclear whether the phosphate directly react with electrode like H 2 O. Herein, the porous and defective Ni(OH) 2 permselective membrane covered Pt and Ni electrode was fabricated by the electrodeposition method to identify the reaction mechanism. By obviously rejecting the phosphate and almost unimpededly transferring the OH−, H 2 O and H 2 , the membrane averts the contact of phosphate with the electrode surface without impeding of the necessary mass transfer of HER. Combining electrochemical analysis and theoretical calculation, the phosphate is found to be the HER reactant of Pt and Ni electrode in PBS. Detailly, the phosphate competes with H 2 O and accelerates the HER for Pt electrode, while poisons Ni electrode to deteriorate the HER performance. The Ni(OH) 2 membrane covered on HER electrode obviously rejects the transfer of phosphate, but almost unimpededly transfer the OH−, H 2 O and H 2 depending on the porous structure. These unique permselective feature helps to identify the HER mechanism in phosphate buffer solution. [Display omitted] [ABSTRACT FROM AUTHOR]