Hydrogen Evolution in Neutral Media by Differential Intermediate Binding at Charge‐Modulated Sites of a Bimetallic Alloy Electrocatalyst

Abstract The energy barrier to dissociate neutral water has been lowered by the differential intermediate binding on the charge‐modulated metal centers of Co 85 Mo 15 sheets supported on Ni‐foam (NF), where the overpotential for hydrogen evolution reaction (HER) in 1 M phosphate buffer solution (PBS) is only 50±9 mV at −10 mA cm −2 . It has a turnover frequency (TOF) of 0.18 s −1 , mass activity of 13.2 A g −1 at −200 mV vs . reversible hydrogen electrode (RHE), and produces 16 ml H 2 h −1 at −300 mV vs . RHE, more than double that of 20 % Pt/C. The Mo δ+ and Co δ− sites adsorb OH*, and H*, respectively, and the electron injection from Co to H−O−H cleaves the O−H bond to form the Mo−OH* intermediate. Operando spectral analyses indicate a weak H‐bonded network for facilitating the H 2 O*/OH* transport, and a potential‐induced reversal of the charge density from Co to the more electronegative Mo, because of the electron withdrawing Co−H* and Mo−OH* species. Co 85 Mo 15 /NF can also drive the complete electrolysis of neutral water at only 1.73 V (10 mA cm −2 ). In alkaline, and acidic media, it demonstrates a Pt‐like HER activity, accomplishing −1000 mA cm −2 at overpotentials of 161±7, and 175±22 mV, respectively.