Single-Layer GaInSe3: Promising Water-Splitting Photocatalyst with Solar Conversion Efficiency over 30% from Theoretical Calculations.

Hydrogen energy from solar water-splitting is known as an ideal method with which to address the energy crisis and global environmental pollution. Herein, the first-principles calculations are carried out to study the photocatalytic water-splitting performance of single-layer GaInSe3 under biaxial strains from -2% to +2%. Calculations reveal that single-layer GaInSe3 under various biaxial strains has electronic bandgaps ranging from 1.11 to 1.28 eV under biaxial strain from -2% to +2%, as well as a completely separated valence band maximum and conduction band minimum. Meanwhile, the appropriate band edges for water-splitting and visible optical absorption up to ~3 × 105 cm-1 are obtained under biaxial strains from -2% to 0%. More impressively, the solar conversion efficiency of single-layer GaInSe3 under biaxial strains from -2% to 0% reaches over 30%. The OER of unstrained single-layer GaInSe3 can proceed without co-catalysts. These demonstrate that single-layer GaInSe3 is a viable material for solar water-splitting.

ZnGeSe2 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 ZnGeSe2 monolayer was explored via first-principles calculations. Our calculated results reveal that the ZnGeSe2 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 ZnGeSe2 monolayer are separately distributed because of the intrinsic dipole. The calculated band edges of the ZnGeSe2 monolayer are demonstrated to be favorable for solar water-splitting. Additionally, the ZnGeSe2 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 ZnGeSe2 monolayer reaches up to 32%, far exceeding the economic value (10%). In light of these hallmarks, the ZnGeSe2 monolayer is demonstrated as an excellent water-splitting photocatalyst.