Tuning Crystallinity Of Rock-Salt Oxides To Optimize E_g Occupancy For Efficient Oxygen Electrocatalysis

Zn-Air battery is a highly efficient energy storage device,but it is restricted by the high overpotential and slow kinetics.It is of great significance to find catalyst with biofunctional OER/ORR activity.Eg filling is related to the binding strength of M-O,which influence the formation of intermediate product,so it is promising to obtain efficient OER/ORR catalyst through modification of e_g.However,the activity of reported work about e_g is poor,and the ways to tune the spin state is limited.Therefore,we use CoNiO₂ by regulating its spin state through crystallinity to acquire efficient oxygen catalytic performance,the results and innovations are as followes:?i?Here we use the solvothermal method to adjust the volume fraction of oleylamine to get CoNiO₂ with adjustable crystallinity and with adjustable electron filling.The method is simple and effective in controlling the e_g of materials with rock-salt-structure.?ii?The CoNiO₂ with a crystallinity of 52.9%and an e_g filling of 1.2 shows the best OER/ORR performance.And the oxygen electrocatalytic activity shows a striking volcano with the e_g filling number of Co²⁺.Excluding the effects of composition,particle size,specific surface area and valence state,the e_g filling number tuned by crystallinity is the main reason that influence the activity of difficient CoNiO₂ catalysts,which is also proved by the annealing experiment.?iii?It is proved that the e_g theory is equally applicable to CoNiO₂ with rock salt structure,and the performance of CoNiO₂ is the best of all the reported catalyst with e_g filling of 1.2,the overpotential of the best CoNiO₂ catalyst for OER is 269 mV,superior than commercial Ir/C and RuO₂,and the onset and half-wave potential of the best CoNiO₂ catalyst for ORR is 935 mV and 837 mV,respectively,which is comparable to commercial Pt/C.This biofunctional catalyst can be integrated into Zn-air batteries.As a result,the CoNiO₂-based battery exhibits superior charge and discharge performance compared to Pt-RuO₂ pair-based battery.