Accelerated kinetics of alkaline hydrogen evolution/oxidation reactions on dispersed ruthenium sites through N and S dual coordination

Efficient, robust and cost-effective electrocatalysts that catalyze hydrogen evolution/oxidation reaction (HER/HOR) in alkaline media are highly demanded. Recently, single-atom catalysts (SACs) have emerged as new promising candidates; however, the rational design of supports and the optimization of coordination environment between supports and metal atoms are challenging. In this work, we successfully fabricate atomically dispersed ruthenium (Ru) species, which are strongly coordinated by N and S dual heteroatoms on holey graphene (RuSA/NSG), as an excellent bifunctional catalyst for HER/HOR. In alkaline media, the developed catalyst exhibits high catalytic performance with a low overpotential of 57.3 mV to drive a current density of 10 mA cm(-1) for HER, and its mass activity is about 5.8 times higher than that of commercial Pt/C and Ru/C catalysts at an overpotential of 100 mV. Similarly, considerable HOR performance of RuSA/NSG is verified to be superior to Pt/C and Ru/C. Furthermore, X-ray-based spectroscopy measurements and density-functional theory calculations have confirmed that, compared with Ru-N-4, the tailored Ru-N-4-S-2 with nearby S dopants can act as more active centers to greatly accelerate the sluggish HER/HOR kinetics in alkaline media. The present work provides a new atomic-level engineering strategy to modulate catalytic activities of SACs via the coordination design using dual heteroatoms on the carbon support.

Automated summary

In this work, atomically dispersed ruthenium species coordinated by N and S dual heteroatoms on holey graphene (RuSA/NSG) were successfully fabricated and demonstrated to be an excellent bifunctional catalyst for hydrogen evolution/oxidation reactions (HER/HOR) in alkaline media. The catalyst exhibited high catalytic performance with low overpotential and its mass activity was significantly higher than that of commercial Pt/C and Ru/C catalysts. The tailored Ru-N-4-S-2 coordination design was found to greatly accelerate the HER/HOR kinetics in alkaline media.