Metal-organic framework-derived Zn_0.975Co_0.025S/CoS₂ embedded in N,S-codoped carbon nanotube/nanopolyhedra as an efficient electrocatalyst for overall water splitting

The development of high-efficiency, low-cost and stable bifunctional electrocatalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is extremely crucial to promote sustainable energy technologies, yet remains a long and arduous challenge. In this work, Zn and Co bimetallic zeolitic imidazolate framework (ZnCo-ZIF) templates were used to synthesize Zn_0.975Co_0.025S/CoS₂ nanoparticles embedded in N,S-codoped carbon nanotube/nanopolyhedra (ZnCoS-NSCNT/NP) via a facile two-step method. Benefitting from the synergetic effect of two metal sulfide species, mesoporous polyhedral structure, N,S-codoped carbon matrix and deep-rooted CNT networks, the product exhibits excellent catalytic performance for both the HER and OER in 1 M KOH, affording a low overpotential of 270 mV for the OER and 152 mV for the HER at a current density of 10 mA cm^-2. More importantly, by utilizing ZnCoS-NSCNT/NP as the electrocatalyst for both the cathode and anode in an electrolyzer for overall water splitting, a current density of 10 mA cm^-2 at 1.59 V and long-term durability (40 h) were achieved. This work opened a new possibility for exploring non-precious-metal catalysts for overall water splitting.