One-step electrodeposition of NiS heterostructures on nickel foam electrodes for hydrogen evolution reaction: On the impact of thiourea content

Herein, we report on the one-step growth of nickel sulfide (NiS) heterostructures on nickel foam (NF) substrate via a facile electrodeposition method, employing Ni(NO3)2 & sdot;6H2O and CH4N2S as Ni and S precursors, respectively. For the first time, a systematic study was carried out on the impact of the Ni/S molar ratio on the electrochemical performance of as-prepared electrodes for water splitting. The optimum performance was obtained for a Ni:S ratio equal to 2:1, whereas lower or higher ratios resulted in much inferior performance. The NiS@NF electrode with a Ni:S ratio of 2:1 exhibited the lowest overpotentials |eta 10| = 136 mV, |eta 100| = 209 mV, extremely low Tafel slope (60 mV dec-1), and very high double layer capacitance value (2.78 mF cm-2). Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and Xray photoelectron spectroscopy (XPS) revealed the formation of a coral-like nanoarchitecture, resulting in enhanced HER activity.