Enhancing photocatalytic water splitting via GeC/SGaSnP Z-scheme heterojunctions with built-in electric fields†

Abstract

Effective photocatalysts are essential for hydrogen production through water splitting. In this study, we predict a Z-scheme heterojunction composed of GeC and Janus SGaSnP monolayers. Binding energy analysis reveals that the heterojunction exhibits excellent thermodynamic stability, particularly in the B- and D-stacking configurations. The electronic structure of the heterojunction reveals strong charge separation and migration properties, driven by the built-in electric field and Janus monolayer polarization, effectively suppressing carrier recombination. Optical absorption and free energy calculations indicate strong visible light absorption, with low hydrogen evolution reaction (HER) free energy barriers of 0.23 eV for both B- and D-stacking configurations. The oxygen evolution reaction (OER) energy barriers are close to the theoretical minimum, at 1.44 eV and 1.48 eV, respectively. Nonadiabatic molecular dynamics (NAMD) simulations show extended electron and hole transfer times, highlighting the potential for efficient photocatalytic hydrogen and oxygen generation. These results suggest the GeC/SGaSnP Z-scheme heterojunction is a promising candidate for advancing photocatalytic water-splitting technologies, with strong catalytic performance and stability.