Tailoring the spin state of active sites in amorphous transition metal sulfides to promote oxygen electrocatalysis

Spin regulation of active sites is sparking much interest in boosting oxygen electrocatalytic performance. However, in amorphous electrocatalysts, the design principle of spin regulation to promote catalytic activity remains unclear. Herein, we synthesized a series of heteroatom-doped amorphous transition metal sulfides with regulated spin states using a one-step hydrothermal process. Especially in Mo-doped CoS, the spin state of Co 2+ was successfully modulated to the low-spin state, which could optimize the adsorption free energy of various intermediates, improving the oxygen reduction reaction kinetics. The fabricated Zn-air batteries (ZABs) delivered good cycle stability (over 100 h). The large ZAB (100 cm 2 ) exhibited a high discharge voltage (1.25 V under 0.5 A) and a superior overall mass-energy density (93 W h kg −1 ), which illuminated a 2.5-m light-emitting-diode ribbon for over seven days. This work provides new insight into the mechanism of engineering spin states in amorphous materials for oxygen electrocatalysis.