Electrochemical hydrogen evolution reaction efficiently catalyzed by Ru–N coupling in defect-rich Ru/g-C3N4 nanosheets

Abstract

The low intrinsic activity of Ru seriously restricts its practical application in hydrogen generation (HER) via sustainable water splitting. Herein, we report robust and reliable defect-rich Ru/g-C₃N₄ nanosheet catalysts for electrochemical hydrogen generation both in alkaline and acidic electrolytes. The catalyst can be fabricated by facile pyrolysis of the freeze-dried Ru³⁺–melamine complex, and efficient Ru–N coupling was demonstrated by some spectroscopic characterizations. Theoretical analysis revealed efficient orbital hybridization of Ru and N for Ru–N bond formation in the system, and thereby favorable electron transfer and intermediate adsorption property. As a result, the proposed catalysts exhibited small overpotentials of 27 mV and 34 mV in acidic and alkaline electrolytes, respectively, to achieve 10 mA cm⁻², when loaded on an inert glassy carbon electrode, which ranked among the top Ru-based catalysts. It also exhibited high catalytic stability including 10 000 CV cycles in the dynamic stability study and 20 hours of steady-state operation. The multiple fold increase in intrinsic activity over Ru/C was indicated by specific activity, mass activity, and turnover frequency values; rapid charge transfer, faster kinetics and increased active site exposure were also observed on this catalyst system due to the efficient Ru–N coupling. The current work reports a facile approach for Ru–N coupling structure fabrication and its contribution to the high HER performance, which is conducive to the development of high-performing Ru-based catalysts.