MoS₂ Nanoflowers as a Gateway for Solar-Driven CO₂ Photoreduction

Abstract

The layering of transition metal dichalcogenides (TMD) has revealed engineering opportunities for optoelectronics, field emitter, and photocatalysis applications. Precise and controlled intrinsic material property combinations is needed for visible light photocatalysis optimization, which we demonstrate in this work with MoS2 nanoflowers containing abundant edge plane flakes for CO2 photoreduction optimization. This is the first time controlled imperfections and flake thickness through facile chemical vapor deposition (CVD) synthesis were demonstrated on the nanoflowers, revealing the tuning ability of flake edge morphology, nanoflower size, stacked-sheet thickness, optical band gap energy (Eg), and catalytic function. These influences facilitated Eg tuning from 1.38 to 1.83 eV and the manifestation of the 3R phase prompting improvement to the catalytic behavior. The “sweet spot” of higher catalytic activity during photoreduction experiments was found in those with plentiful nanoflower density and thick edge-site abundance. Ample edge sites with dangling bonds and crystal impurities assisted in lowering the Eg to achieve reduced recombination for improved photocatalytic reactions, including those found on what would have been a chemically inert basal plane. The production rates of CO improved 2-fold after a calculated post-treatment reduction step. This reliable CVD technique for nanoflower synthesis paves the way for enhanced understating of synthetic parameters for defect-laden 2D TMD nanoflower structures. This work contributes to the development of efficient and stable photocatalytic materials for CO2 conversion from abundant elements, at levels suitable for Mars exploration.