Anion substitution induced vacancy regulating of cobalt sulfoselenide toward electrocatalytic overall water splitting.

Herein, the relationship between vacancy concentration and electrocatalytic water splitting performance has been investigated. The CoS1.25Se0.75@NC possesses the largest vacancy concentration as well as the optimal electrocatalytic performance. [Display omitted] Anion substitution is a valid strategy to modulate the active sites of the transition metal dichalcogenides (TMDs). Herein, a series of cobalt sulfoselenide nanomeshes (CoS 2(1-x) Se 2x @NC) were synthesized by calcining S/Se power with ultrathin metal–organic framework (MOFs) nanosheets. The vacancy concentration of CoS 2(1-x) Se 2x @NC could be adjusted through changing the ratio of S/Se precursor. Interestingly, CoS1.25Se0.75@NC electrocatalyst possesses the largest vacancy concentration as well as the optimal electrocatalytic performance. CoS 1.25 Se 0.75 @NC delivers an overpotential as low as 134 mV for hydrogen evolution reaction (HER) and 270 mV for oxygen evolution reaction (OER) at the current density of 10 mA cm -2, respectively. Furthermore, CoS 1.25 Se 0.75 @NC affords a low cell voltage of 1.67 V (at 10 mA cm−2) and outstanding cycling stability for overall water splitting reaction (more than 55 h). For HER process, theoretical calculations prove that anion vacancy not only lower the free energy barrier of H 2 O dissociation step but also favor the desorption step of intermediate H*. For OER process, the anion vacancies could modulate the adsorption/desorption free energy of oxygen-containing intermediates. The present work demonstrates a practical approach to modulate the vacancy concentration of cobalt sulfoselenide and provides new ideas for design of efficient non-metal electrocatalysts. [ABSTRACT FROM AUTHOR]