Porphyrin coordination polymer supported transition-metal sulfides as precious-metal-free electrocatalysts for efficient overall water splitting.

The electrochemical water splitting in strongly acidic medium with noble-metal-free electrocatalysts remains a desirable yet technological challenge. Herein, we developed a series of porphyrin coordination polymer supported transition-metal sulfides as bifunctional electrocatalysts (Co 3 S 4 @MoS 2 @nTiPCP, n = 10, 20 or 30) that performs well in acidic media. The optimal Co 3 S 4 @MoS 2 @20TiPCP achieves current densities of 10 mA cm−2 at overpotentials of 247 and 110 mV for acidic OER and HER, respectively. Particularly, an electrolyzer with better long-term stability using Co 3 S 4 @MoS 2 @20TiPCP as both cathode and anode exhibits a low cell voltage of 1.41 V at 10 mA cm−2 in acid, outperforming most other reported electrocatalysts elsewhere. The efficient electrochemical water splitting is ascribed to the synergetic effect and the unique structure characteristics. DFT calculations demonstrate that the Co atoms in Co 3 S 4 @MoS 2 @20TiPCP are the major active sites for electrochemical water splitting thanks to regulated electronic structures and reduced reaction energy barrier. Porphyrin coordination polymer supported transition-metal sulfides exhibit effective overall water splitting in acidic media, due to the synergetic effect between each component and the unique structure characteristics. [Display omitted] • Porphyrin coordination polymer supported metal sulfides as were prepared. • The samples show efficient acidic water electrooxidation. • The efficient acidic electrochemical water splitting is also observed. [ABSTRACT FROM AUTHOR]