Metal hydroxide salt monolayer nanoparticles: synthesis, redox characterization, and electrochemical catalytic performance

Two-dimensional materials modified with low molecular weight species are known to show unique electronic properties. In this study, we focus on the synthesis and electrochemical investigation of metal hydroxide salt monolayer nanoparticles modified with different molecules toward improved electrochemical functions. Nickel hydroxide carboxylate nanoparticles were successfully prepared through the epoxide-mediated alkalinization method using alkylcarboxylates. It was found that the monolayer nanoparticles with a size of approximately 2 nm were formed directly from an ionic precursor or after ultrasonication post-treatment. Manganese, iron, and cobalt hydroxide carbonates were found to form monolayer nanoparticles through the same procedure. Synthesized nickel hydroxide carbonate monolayer nanoparticles with a short alkylcarboxylate showed enhanced redox processes and electrochemical functions due to higher proton diffusion coefficient, lower electron transfer resistance, and improved intrinsic catalytic activity. We propose that the results obtained in this study will provide a novel design strategy for metal hydroxide monolayer nanoparticulate catalysts toward high functionality.This work was supported by JSPS KAKENHI (Grant Numbers JP20K15368, JP21H00149, JP22K14753, and JP22H05143), JSPS Core-to-Core Program, MEXT Leading Initiative for Excellent Young Researchers, MEXT Strategic Professional Development Program for Young Researchers (HIRAKU-Global), the Cooperative Research Program of Institute for Catalysis, Hokkaido University (Grant number 21A1007), the facilities of the Institute of Materials and Systems for Sustainability, Nagoya University, Iketani Science and Technology Foundation, and the Takahashi Industrial and Economic Research Foundation