Atomistic insights into highly active reconstructed edges of monolayer 2H-WSe₂ photocatalyst

Ascertaining the function of in-plane intrinsic defects and edge atoms is necessary for developing efficient low-dimensional photocatalysts. We report the wireless photocatalytic CO₂ reduction to CH₄ over reconstructed edge atoms of monolayer 2H-WSe₂ artificial leaves. Our first-principles calculations demonstrate that reconstructed and imperfect edge configurations enable CO₂ binding to form linear and bent molecules. Experimental results show that the solar-to-fuel quantum efficiency is a reciprocal function of the flake size. It also indicates that the consumed electron rate per edge atom is two orders of magnitude larger than the in-plane intrinsic defects. Further, nanoscale redox mapping at the monolayer WSe₂-liquid interface confirms that the edge is the most preferred region for charge transfer. Our results pave the way for designing a new class of monolayer transition metal dichalcogenides with reconstructed edges as a non-precious co-catalyst for wired or wireless hydrogen evolution or CO₂ reduction reactions.