NiCo<sub>2</sub>O<sub>4</sub>‐Based Nanosheets with Uniform 4 nm Mesopores for Excellent Zn–Air Battery Performance
Jie Yin, Jing Jin, Hongbo Liu, Bolong Huang, Min Lu, Jianyi Li, Hanwen Liu, Hong Zhang, Yong Peng, Pinxian Xi, Chun‐Hua Yan
Abstract
Abstract Herein, a strategy is reported for the fabrication of NiCo 2 O 4 ‐based mesoporous nanosheets (PNSs) with tunable cobalt valence states and oxygen vacancies. The optimized NiCo 2.148 O 4 PNSs with an average Co valence state of 2.3 and uniform 4 nm nanopores present excellent catalytic performance with an ultralow overpotential of 190 mV at a current density of 10 mA cm −2 and long‐term stability (700 h) for the oxygen evolution reaction (OER) in alkaline media. Furthermore, Zn–air batteries built using the NiCo 2.148 O 4 PNSs present a high power and energy density of 83 mW cm −2 and 910 Wh kg −1 , respectively. Moreover, a portable battery box with NiCo 2.148 O 4 PNSs as the air cathode presents long‐term stability for 120 h under low temperatures in the range of 0 to −35 °C. Density functional theory calculations reveal that the prominent electron exchange and transfer activity of the electrocatalyst is attributed to the surface lower‐coordinated Co‐sites in the porous region presenting a merging 3d–e g –t 2g band, which overlaps with the Fermi level of the Zn–air battery system. This favors the adsorption of the *OH, and stabilized *O radicals are reached, toward competitively lower overpotential, demonstrating a generalized key for optimally boosting overall OER performance.