Effect of charge state on alkaline OER activity in FeN4−Gr catalyst supported on Ni (111) substrate

Abstract The catalysts of transition metal single–atom embedded in N–doped graphene (TMN 4 –Gr) have attracted significant attention due to the high utilization of transition metal atoms, remarkable selectivity and tunable catalytic activity. In this study, we have employed first–principles study to investigate alkaline oxygen evolution reaction (OER) activity of FeN 4 –Gr system supported on a Ni (111) substrate (FeN 4 –Gr/Ni). The results show that the Ni substrate can significantly enhance the OER activity of FeN 4 –Gr catalyst. The overpotential of FeN 4 –Gr/Ni catalyst is 0.63 V, much lower than 0.79 V of the FeN 4 –Gr, which is closely related to the strong interaction from the Ni substrate. By subtracting electrons from the FeN 4 –Gr/Ni catalyst, a positive charge environment can be created. It is found that, between the FeN 4 –Gr and the Ni substrate, a significant electron transfer phenomenon is observed, and the amount can be regulated by the charge state. Besides, the charge state can obviously tune the adsorption strength of *OOH intermediate through the interaction of Ni substrate, further optimizing the OER activity thermodynamically favorable. As the charge state increases to +1.55, the overpotential decreases to 0.23 V. By analyzing the integrated crystal orbital Hamilton populations, the chemical bond strength of Fe–O is discussed. Our results reveal that the Ni substrate can significantly enhance the OER activity of the FeN 4 –Gr catalyst, and the charge state can also tune the overpotential, offering valuable insights for the design of high–efficiency single–atom catalysts utilizing metal substrate.