Amorphous Ni x Co y P-supported TiO 2 nanotube arrays as an efficient hydrogen evolution reaction electrocatalyst in acidic solution.

Bimetallic phosphides have been attracting increasing attention due to their synergistic effect for improving the hydrogen evolution reaction as compared to monometallic phosphides. In this work, NiCoP modified hybrid electrodes were fabricated by a one-step electrodeposition process with TiO2 nanotube arrays (TNAs) as a carrier. X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy and scanning transmission electron microscopy/energy-dispersive X-ray spectroscopy were used to characterize the physiochemical properties of the samples. The electrochemical performance was investigated by cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. We show that after incorporating Co into Ni-P, the resulting Ni x Co y P/TNAs present enhanced electrocatalytic activity due to the improved electron transfer and increased electrochemically active surface area (ECSA). In 0.5 mol L-1 H2 SO4 electrolyte, the Ni x Co y P/TNAs ( x = 3.84, y = 0.78) demonstrated an ECSA value of 52.1 mF cm-2 , which is 3.8 times that of Ni-P/TNAs (13.7 mF cm-2 ). In a two-electrode system with a Pt sheet as the anode, the Ni x Co y P/TNAs presented a bath voltage of 1.92 V at 100 mA cm-2 , which is an improvment of 79% over that of 1.07 V at 10 mA cm-2 .