Optimizing strong metal-support interaction on cobalt phosphide-supported Ru single atom catalyst for highly-efficient hydrogen evolution reaction

The increasingly severe environmental problems urge human beings to develop clean energy to replace the traditional fossil-based energy. "Green hydrogen", which is generated from water by renewable energy, is one such promising candidate; however, its wide production is seriously hindered by the scarce and expensive Pt-based electrocatalysts currently used. In dealing with this demand, we recently developed a novel cobalt phosphide-based Ru single-atom electrocatalyst (Ru-SA@CoPx) for hydrogen evolution reaction (HER). Characterizations revealed that the atomically dispersed Ru atoms could induce charge transfer to the CoPx support, which was composed of CoP and Co2P, thereby generating a strong metal-support interaction (SMSI). It was also found that the SMSI could be tuned by temperature, rendering Ru-SA@CoPx-350 with an overpotential of 26 mV to deliver a current density of 10 mA cm(-2) for HER in alkaline medium, which was superior to the commercial Pt. Density functional theory calculations showed that the Ru single-atom could drastically reduce the energy barrier for water dissociation, leading to a more favorable Volmer step than for Pt. Further study revealed that the charge transfer from Ru to CoP(200) was disadvantageous to HER because of the exacerbated H* adsorption strength; whereas, the slightly negatively charged Ru could help to achieve a more thermoneutral adsorption energy on the Co site in Ru-Co2P(111). This study provides a promising strategy for tuning the SMSI effect in the development of highly efficient single-atom catalysts.