Anchoring Ru nanoclusters to defect-rich polymeric carbon nitride as a bifunctional electrocatalyst for highly efficient overall water splitting

Abstract

Developing a cost-effective and highly efficient electrocatalyst for the hydrogen economy remains a significant challenge due mainly to the high overpotentials of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we propose an effective modification strategy by encapsulating a small amount of Ru nanoclusters (NCs) into g-C₃N₄ rich in N-vacancies (V_N). Systematic experiments were carried out to investigate the formation process of Ru NCs and demonstrate the strong interaction between Ru NCs and substrates. The optimized Ru NCs/V_N-C₃N₄ displays a unique porous structure along with plentiful defects, maximizing the exposure of the active sites. As expected, Ru NCs/V_N-C₃N₄ presents a preferable electrocatalytic activity with an overpotential of 8 mV for the HER and 200 mV for the OER at a current density of 10 mA cm⁻², along with an ultra-high mass activity of Ru. DFT calculations further substantiate the superior HER and OER performance of Ru NCs/V_N-C₃N₄, and confirm that the introduction of abundant V_N effectively modulates the d-band center, intermediate binding energies and structural stability. When integrated into a symmetric electrolyzer, the cell voltage remarkably reduces to 1.488 V with splendid stability in alkaline medium, outperforming nearly all commercial electrocatalysts. This work sheds light on a novel avenue for the rational design of new-generation bifunctional electrocatalysts to promote the popularization of the hydrogen economy.