Insight into improved oxygen evolution reaction on electronic modulation of phosphorus doped NiCo2O4

In this work, we report the fabrication of phosphorus doped NiCo2O4 (P-NiCo2O4) to achieve the development of oxygen evolution reaction (OER) catalysts. The obtained 1% P-NiCo2O4 exhibited better OER activity than that of pure NiCo2O4 with an overpotential of 370 mV at 10 mA cm-2, a high Cdl value of 41.8 mF cm-2, a small Tafel slope value of 95 mV dec-1, as well as remarkable stability. The superior electrochemical performances could be attributed to the formed mipor layer, resulting in the acceleration of the diffusion speed of electrolyte or ions on the interface between liquid and electrode. The correlation of experiments and DFT calculation results revealed that due to P doping, the electron density of Co and Ni around replaced O atom increased, leading to the higher ratio of Co3+/Co2+ and Ni3+/Ni2+, which is beneficial to the rate-determining step (RDS) of transformation of HO* to O*. The calculated maximum Delta G of RDS are 1.68 eV and 1.54 eV for NiCo2O4 and P-NiCo2O4, respectively, demonstrating the better OER performance of P-NiCo2O4.