S-doped carbonized wood fiber decorated with sulfide heterojunction-embedded S, N-doped carbon microleaf arrays for efficient high-current-density oxygen evolution

Industrial high-current-density oxygen evolution catalyst is the key to accelerating the practical application of hydrogen energy. Herein, Co9S8/CoS heterojunctions were rationally encapsulated in S, N-codoped carbon ((Co9S8/CoS)@SNC) microleaf arrays, which are rooted on S-doped carbonized wood fibers (SCWF). Benefiting from the synergistic electronic interactions on heterointerfaces and the accelerated mass transfer by array structure, the obtained self-supporting (Co9S8/CoS)@SNC/SCWF electrode exhibits superior performance toward alkaline oxygen evolution reaction (OER) with an ultra-low overpotential of 274 mV at 1000 mA/cm2, a small Tafel slope of 48.8 mV/dec, and ultralong stability up to 100 hours. Theoretical calculations show that interfacing Co9S8 with CoS can upshift the d-band center of the Co atoms and strengthen the interactions with oxygen intermediates, thereby favoring OER performance. Furthermore, the (Co9S8/CoS)@SNC/SCWF electrode shows outstanding rechargeability and stable cycle life in aqueous Zn-air batteries with a peak power density of 201.3 mW/cm2, exceeding the commercial RuO2 and Pt/C hybrid catalysts. This work presents a promising strategy for the design of high-current-density OER electrocatalysts from sustainable wood fiber resources, thus promoting their practical applications in the field of electrochemical energy storage and conversion.