Electrochemical and kinetic studies of chemical vapor deposition (CVD)-processed carbon-doped nickel for hydrogen evolution reaction (HER)

Abstract

In this study, carbon-doped nickel (C–Ni) was synthesized via CVD at different synthesis temperatures (700 °C, 800 °C, and 900 °C) to investigate the effect of temperature on material structure and HER performance in acidic media. At 700 °C, the C–Ni surface featured amorphous carbon layers, while higher temperatures promoted increased graphitization, with crystalline carbon observed at 900 °C. Electrochemical testing in 0.5 M H2SO4 revealed overpotentials of −268 mV, −279 mV, and −295 mV at 10 mA/cm2 for C–Ni synthesized at 700 °C, 800 °C, and 900 °C, respectively. Tafel slope analysis demonstrated improved HER kinetics at lower synthesis temperatures. C–Ni@700 °C achieved the lowest slope of −85 mV·dec−1 at low current densities. FEM simulations supported the experimental findings, illustrating enhanced charge distribution (V–H–T mechanism) and current density uniformity. These results confirm that lower synthesis temperatures favour the formation of carbon structures enhancing catalytic activity. This work provides insights into temperature-controlled synthesis of C–Ni catalysts for hydrogen generation.