ZnGeSe 2 monolayer: water-splitting photocatalyst with ultrahigh solar conversion efficiency.

Hydrogen production through solar water-splitting offers a clean and renewable solution to tackle the ongoing issues of energy scarcity and environmental pollution. Here, the solar water-splitting performance of the ZnGeSe 2 monolayer was explored via first-principles calculations. Our calculated results reveal that the ZnGeSe 2 monolayer embodies stable configurations and semiconducting properties with direct bandgaps ranging from 1.23 to 1.60 eV under the biaxial strain from -1% to +2%. The generated holes and electrons of the ZnGeSe 2 monolayer are separately distributed because of the intrinsic dipole. The calculated band edges of the ZnGeSe 2 monolayer are demonstrated to be favorable for solar water-splitting. Additionally, the ZnGeSe 2 monolayer exhibits strong optical absorption in the whole visible region. The hydrogen and oxygen evolution reactions can be accomplished without cocatalysts. Of particular significance, the solar to hydrogen (STH) efficiency of the ZnGeSe 2 monolayer reaches up to 32%, far exceeding the economic value (10%). In light of these hallmarks, the ZnGeSe 2 monolayer is demonstrated as an excellent water-splitting photocatalyst.