Phosphorous doped cobalt-iron sulfide/carbon nanotube as active and robust electrocatalysts for water splitting

Abstract Earth-abundant water splitting electrocatalysts with high activity and robust stability are in great demand for realizing efficient sustainable energy conversion and storage. Here, we propose a multi-elements composition-engineering approach to construct phosphorous (P) doped cobalt iron sulfide (CoFeS) hybrids for efficient water electrocatalysis. Through the combination of Co and P co-doping, nanostructuring, and hybridization with carbon nanotubes (CNTs), we demonstrate that the designed CoFeSP/CNT with optimum composition is superior bifunctional electrocatalyst for both hydrogen and oxygen evolution reaction (HER and OER). When employed as a hydrogen-evolution electrode, the as-synthesized CoFeSP/CNT are found to be stable and active in both acid and alkaline electrolytes. When used as an oxygen-evolution electrode, the in-situ electrochemical generated CoFe-oxyhydroxides exhibits excellent performance where low overpotentials of 262 and 309 mV achieved at a current density of 10 and 100 mA cm −2 , respectively. Moreover, a two-electrode alkaline water electrolyzer constructed with three dimensional CoFeSP nanorods on carbon cloth (CoFeSP/CC) can afford a current density of 50 mA cm −2  at a voltage of 1.62 V.