Buckled arsenene monolayer as an efficient water-splitting photocatalyst

Two-dimensional (2D) semiconductors have emerged as promising photocatalysts for sustainable hydrogen production. In this work, we employ the density functional theory to investigate the structural, electronic, and catalytic properties of a buckled arsenene (As) monolayer as a candidate photocatalyst for water splitting. Structural optimization and phonon dispersion analyses confirm the dynamic stability of the buckled configuration, consistent with bulk gray arsenic. The As monolayer exhibits an indirect bandgap of 1.73 eV, ideally positioned for visible-light absorption and effective separation of photogenerated carriers. Projected density of states analysis reveals strong orbital contributions near the band edges that enhance photocatalytic activity. To assess hydrogen evolution reaction performance, hydrogen adsorption was systematically studied at different sites on the As surface. The computed adsorption energy (−1.96 eV) and Gibbs free energy (−1.72 eV) indicate highly favorable chemisorption and efficient catalytic behavior, with band structure modifications confirming metallicity upon hydrogen adsorption. Increasing hydrogen coverage further demonstrated spontaneous adsorption and robust catalytic activity. Collectively, these findings establish the buckled As monolayer as a stable, visible-light-responsive, and highly active photocatalyst, highlighting its strong potential for water-splitting applications and renewable hydrogen generation.