2D-GaS as a Photocatalyst for Water Splitting to Produce H₂

Using first-principles local and hybrid density functional theoretical calculations, a thickness-dependent electronic structure of layered GaS is determined, and it is shown that 2D GaS has an electronic structure with valence and conduction bands that straddle the redox potentials of hydrogen evolution reaction and oxygen evolution reaction up to a critical thickness (<5.5 nm). Here, simulations of adsorption of H2O on nanoscale GaS reveal that localized electronic states at its edges appear in the gap and strengthen the interaction with H2O, further activating the surface atomic sites. It is thus predicted that GaS synthesized with a controlled thickness and preferred edges may be an efficient catalyst for photocatalytic splitting of water. Experiments that verify some of the predictions in this study are presented, and it is shown that GaS is effective in absorption of light and evolution of H2 (887 μmol h−1 g−1) in the presence of aqueous solution of hydrazine (1% v/v). This study should open up the use of nanoscale GaS in conversion of solar energy into environment-friendly chemical energy in the form of hydrogen.