Charge regulation engineering to suppress Jahn-Teller distortion in low crystallinity In-doping MnCo2O4 for high activity pseudocapacitors and hydrogen evolution reaction

Abstract Jahn-Teller distortion in the transition metal oxides (TMOs) could cause the poor activity and stability in the potentially promising materials for the supercapacitor and electrocatalyst. Herein, a novel strategy to address this problem by a charge regulation engineering is provided, in which, the Jahn-Teller distortion in the low crystallinity In-doped MnCo2O4 (In/MnCo2O4) in-situ grown on the Nickel foam (NF) (In/MnCo2O4-NF) by a simple laser-assisted method is significantly reduced. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectrum (XANES) analyses show that the strong electronic interaction between the doped In and Mn/Co suppresses Jahn-Teller distortion of Mn3+ and Co3+ cations in the In/MnCo2O4. Moreover, density functional theory (DFT) calculations reveal that the enhanced electrochemical activity and the effects of suppressed Jahn-Teller distortion. As a result, In/MnCo2O4-NF material shows a highly supercapacitive performance with a high specific capacitance of 1436.8F g−1 at a current density of 1 A g−1, a high rate capability of 71.9% of the capacitance retention at 20 A g−1, and a superior cycle stability (90.1% of the specific capacitance retention after 16,000 cycles). When being paired with activated carbon, the quasi-solid-state asymmetric supercapacitor provides a maximum energy density of 61.5 Wh kg−1 at a power density of 963.2 W kg−1 and an ultra-long cycling lifespan (84.6% retention after 120,000 cycles at 10 A g−1). Furthermore, In/MnCo2O4-NF as an electrocatalyst has a high hydrogen evolution reaction (HER) performance with a low overpotential (61.8 mV) and a small Tafel slope (76 mV dec-1).