Square octagon haeckelites as efficient photocatalysts with enhanced solar-to-hydrogen conversion and high carrier mobilities

The increasing demand for renewable energy solutions underscores the importance of photocatalytic water splitting as a sustainable technology. In this study, we present a first-principles investigation of synthesized novel square-octagon haeckelite AB compounds (A = Sb, Be, Cd, In, Mg, Zn; B = Al, S, Se, Te, P), revealing their superior photocatalytic properties. These 3D materials exhibit unique square-octagonal geometries, optimized band gaps (1.33-3.83 eV), and favorable band edge alignments for water splitting under both acidic (pH = 0) and neutral (pH = 7) conditions. Notably, AlSb achieves the highest solar-to-hydrogen efficiency of 49.00%, followed by CdTe (38.97%), CdSe (18.35%), and InP (38.21%), outperforming conventional photocatalysts. The study also highlights the exceptional carrier mobilities (<i>μ</i>) of AB haeckelite compounds, with ZnTe achieving an electron mobility of 19.3 × 10⁶ cm² V^-1 s^-1 and hole mobility of 24.9 × 10⁴ cm² V^-1 s^-1. These high mobilities facilitate efficient charge transport and minimize recombination losses, enhancing their photocatalytic performance. Additionally, CdTe and CdSe demonstrate strong visible-light absorption, while MgSe and BeSe excel in ultraviolet absorption, showcasing their versatility for optoelectronic applications. This work establishes AB haeckelite compounds as transformative materials for solar-driven hydrogen production by overcoming conventional photocatalysts' limitations, like poor sunlight utilization and low carrier mobility, paving the way for sustainable energy technologies.