Novel Janus silicon-based pentagonal monolayers for enhanced photocatalytic water splitting

Conventional symmetrical two-dimensional materials face limitations in photocatalytic efficiency for water splitting. This study designs asymmetric pentagonal Janus silicon-based monolayers to address this. Using density functional theory, we investigate four configurations: conventional penta-silicon-sulfur-selenium, penta-silicon-selenium-tellurium, and their Janus derivatives. All demonstrate robust stability and suitable bandgaps for solar harvesting. The Janus silicon-selenium-tellurium monolayer exhibits a direct bandgap for efficient carrier generation, while Janus asymmetry induces intrinsic electric fields enhancing charge separation. Penta-silicon-sulfur-selenium shows exceptional visible-light absorption, and Janus structures enable high electron mobility with suppressed recombination. Hydrogen evolution reaction analysis reveals three materials as active under acidic conditions, with two showing superior performance in neutral environments. Titanium doping simultaneously reduces reaction barriers and improves light absorption. Combining the advantages of direct bandgap and strong absorption, these materials offer a promising platform for efficient solar hydrogen production.