Built-in electric field and core-shell structure of the reconstructed sulfide heterojunction accelerated water splitting

The rational design of high-performance bifunctional electrocatalysts for overall water splitting (OWS) is the key to popularize hydrogen production technology. The active metal oxyhydroxide (MOOH) formed after surface self-reconfiguration of transition metal sulfide (TMS) electrocatalyst is often regarded as the "actual catalyst" in oxygen evolution reaction (OER). Herein, an Fe doped CoS₂/MoS₂ hollow TMS polyhedron (Fe-CoS₂/MoS₂) with rich Mott-Schottky heterojunction is reported and directly utilized as an OWS electrocatalyst. The spontaneous built-in electric field (BEF) at the heterogeneous interface regulates the electronic structure and D-band center of the catalyst. More importantly, the “TMS-MOOH” core-shell structure obtained in the KOH electrolyte shows enhanced OER properties. And the introduction of Fe ions activates the inert basal plane of MoS₂, which greatly steps up the performance of HER. Hence, the preferable Fe-CoS₂/MoS₂–400 presents superior OER activity (η₁₀ = 178 mV, η₁₀₀ = 375 mV), HER activity (η₁₀ = 92 mV) and ultra-high stability for 50 h. This work has deeply explored the catalytic mechanism of TMS and provided a new idea for the construction of efficient bifunctional catalysts.