Transition metal chalcogenide nanoparticle embedded metal-organic framework nanosheets for high-performance H₂O₂ electrosynthesis

The rational design of high-performance two-electron oxygen reduction reaction (2e-ORR) electrocatalysts is of great significance for sustainable H₂O₂ production. Herein, we report the synthesis of a transition-metal chalcogenide@metal-organic framework (TMC@MOF) composite material as an efficient 2e-ORR electrocatalyst. Through a partial conversion route using NiFe-MOF nanosheets as precursors, the Ni ions are partially converted into NiS₂ nanoparticles, which are embedded in the MOF skeleton with partially preserved crystalline structure and in situ generated mesopores. Experimental and theoretical results demonstrate that the interaction between NiS₂ and retained MOFs regulates the electronic structure of Ni sites in NiS₂ toward optimized adsorption of oxygen intermediates, enhancing the 2e-ORR selectivity. Additionally, the ultrasmall NiS₂ nanoparticles (grain size < 10 nm) expose abundant active sites, and the created mesopores facilitate the mass transfer. Collectively, excellent 2e-ORR performances are achieved with a high selectivity of 96% and a high H₂O₂ production rate of 4.2 mol g_cat⁻¹ h⁻¹. The proposed partial sulfidation strategy paves the way for the design of advanced MOF-based composite materials for various applications.