Modulating Electronic State and <i>d</i>-Band Center of Mo Atoms for High-Efficient Hydrogen Evolution

Electrocatalysts play a crucial role in efficient hydrogen production through water splitting, and there is significant interest in enhancing their performance via microscopic regulation. In this study, we introduce for the first time a novel series of Mo2C/MoO2/C electrocatalysts enriched with heterojunctions, synthesized using sustainable carbon precursors such as vegetable oil. The incorporation of heterojunctions within these catalysts fine-tunes the electronic structure of Mo atoms, shifting the d-band center to significantly improve catalytic efficiency. The developed Mo2C/MoO2/C electrocatalysts exhibit low overpotentials of 104 mV in 1 M KOH and 141 mV in 0.5 M H2SO4 electrolytes at a current density of 10 mA·cm–2, with Tafel slopes of 67.30 mV·dec–1 and 71.21 mV·dec–1, respectively. These catalysts also show exceptional stability, maintaining their activity for over 30 h under both acidic and alkaline conditions. Density functional theory (DFT) calculations provide insights into the mechanism behind this enhanced performance. They reveal that the adjusted electronic states of Mo atoms and the shifted d-band center optimize the adsorption and desorption dynamics of hydrogen intermediates (H*), thereby significantly boosting the hydrogen evolution reaction (HER) activity. This strategy is universal, as an electrocatalyst prepared using carbon source waste cooking oil also achieves comparable overpotentials of 106 mV in 1 M KOH and 136 mV in 0.5 M H2SO4 at the same current density. It also delivers superior double-layer capacitance values of 112.05 mF·cm–2 and 77.25 mF·cm–2 in the respective electrolyte solutions. This highlights the significant potential of natural carbon precursors for advanced electrocatalyst design.