Designing of highly-efficient OER and ORR transition metal-nitrogen active centers with the aid of the revised d electron density

It is quite important to suggest a suitable modification method for the design of highly-efficient catalysts with the aid of the local atomic structures of active center. In this work, the d electron density (D'd) of transition metal (TM) ions was revised to correlate the local atomic structures and catalytic activity of TM1N4 active centers by introducing the dynamic radius of TM and N ions. Meanwhile, the "volcano" relationship between the OER/ORR potentials and D'd values was acquired to suggest the modification methods. The pressure (tensile) stress would be applied to increase (weaken) the d-p orbital hybrid strength of Fe1-N (Co1-N and Ni1-N) bonds and increase (reduce) the D'd values of Fe1N4 (Co1N4 and Ni1N4) active centers. Based on the theoretical prediction, the Fe1-pyrrolee N4 (0 %) and Fe1-pyrrolee N4 (−2%) active centers respectively exhibited the lowest overpotentials of 213 mV for OER and 189 mV for ORR in this work. Hence, the revised d electron density could be applied for the method of external stress field, and this strategy would be adopted to design more highly-efficient catalysts.