Mesoporous Single Crystal NiS2 Microparticles with FeS Clusters Decorated on the Pore Walls for Efficient Electrocatalytic Oxygen Evolution

Abstract Abundant active sites and their easy accessibility in a stable and conductive structure are of great importance for efficient electrocatalysts. In principle, activated mesoporous single‐crystal microparticles can meet these desired requirements. Here, the Fe‐doped NiS 2 mesoporous single crystal microparticles decorated with FeS clusters on the pore walls (FeS@MSC‐NiS 2 :Fe) are constructed via a pre‐decorated and sequentially seeded mesoporous silica template. Throughout the external and internal surfaces, the Fe‐doped NiS 2 modulated by the adjacent FeS clusters induces favorable charge distributions and promotes the crucial formation of the active Fe/Ni (oxy)hydroxide. Combined with the spatial enrichment effect of the intermediates in the holey space and the boosted charge transfer within the continuous single‐crystalline framework, the dually regulated FeS@MSC‐NiS 2 :Fe as ideal integral microreactors show efficient performances in oxygen evolution reaction. In electrochemical tests, the particulate FeS@MSC‐NiS 2 :Fe requires an overpotential of only 236 mV to reach a current density of 10 mA cm −2 and displays fast reaction kinetics with a Tafel slope of 32.4 mV dec −1 . This study provides an important strategy to construct electrocatalysts with highly active sites and good accessibility.