Synergistic Interactions Enable Superior Oxygen Evolution Reaction Activity in Compositionally Complex Nanocrystal–Nanosheet Hybrids

Abstract Thiospinel nanoparticles are promising catalytic materials due to their compositional tunability, electronic conductivity, and structural stability. While significant gains in catalysis have been made through material engineering, one continuously developing route is through the use of support materials to enhance performance. Here, we report a simple, scalable, low-temperature method to coproduce colloidal multimetal nanocrystals (<20 nm in diameter) and In2S3-based nanosheets (<1 nm thick), forming compositionally complex hybrid nanocrystal–nanosheet heterostructures in situ. The in situ-formed heterostructures demonstrate enhanced catalytic activity in the oxygen evolution reaction (OER) in alkaline conditions; peak performance was achieved in heterostructures formed between (Ni,Co,Fe)3S4 nanocrystals and (In,Fe,Mn)2S3 nanosheets with overpotentials as low as 283 mV at 10 mA/cm2. Heterostructures can also be produced ex situ by introducing nanosheets, postsynthetically, to the nanocrystals, reducing the overpotential of (Ni,Co,Fe)3S4 nanocrystals from 362 mV to 312 mV with only a 5 wt % addition. This improvement highlights synergistic interactions in the heterostructures. These results suggest that an optimum nanosheet loading that maximizes effective nanocrystal–nanosheet interfacial coupling while preserving access to the Ni/Co-rich catalytic domains is the relevant design parameter. Our findings provide a low-temperature, colloidal route for synthesizing compositionally complex and highly uniform (<15% dispersity) sulfide nanocrystals, nanosheets, or heterostructures of the two with tunable structures and enhanced electrocatalytic performance. To our knowledge, this is the first report of a compositionally complex hybrid material that is able to enhance performance when formed both in situ or ex situ and the use of In2S3 as a scaffold for a support material for enhancing OER performance.