Rational insights into the fundamentals of a low density porous framework-N-doped ZnIn2S4 (ZIS) for photocatalytic water splitting using density functional theory calculations

ZnIn 2 S 4 (ZIS) has been a potential candidate these days as a photocatalyst to produce H 2 via the water splitting method. Besides having a suitable band structure and optical and electronic properties, it has notable drawbacks such as low light absorption capacity, high recombination rate, lower water splitting capacity, etc., which have not been given enough attention yet. This study investigated fundamental optical and electronic properties of ZnIn 2 S 4 using density functional theory calculations, and the modification of ZIS with N doping has been considered to predict the performance of ZIS with anion substitution. Starting from a modeled cubic structure, we generated a triclinic, low‑density porous phase denoted Zn 2 In 6 S 8 by cleaving and creating a surface mesh. Partial substitution of In 3 + and In 5+ by N produced the 33% N‑doped structure Zn 2 In 4 N 2 S 8 and 66% N-doped Zn 2 In 2 N 4 S 8, respectively. For clarity, we denote pristine Zn 2 In 6 S 8 as ZINS 2608, 33% N-doped Zn 2 In 4 N 2 S 8 as ZINS 2428, and 66% N-doped Zn 2 In 2 N 4 S 8 as ZINS 2248 throughout the manuscript. This substitution results in a lower material density from 1.235 g/cm³ (ZINS‑2608) to 0.89 g/cm³ (ZINS‑2428), inducing sulfur vacancies, and expands the lattice to form a more porous framework. Afterwards, the energy band structure and density of states were calculated, which indicates that N doping significantly reduced the band gap from 1.49 eV to 1.29 eV in N-ZIS compared to pristine ZIS. Theoretical calculations suggest a higher light absorption profile, and the quantum yield improved to 0.89 and 0.93 from 0.85 compared to pristine ZIS. A water interaction study was also included in the final part of the article, which estimated a higher hydrogen evolution rate of 113.742 µmol g −1 h −1 (ZINS‑2428) compared to 24.06 µmol g −1 h −1 (ZINS 2608) and a significant 7.48% improvement in STH efficiency in N-ZIS compared to only 1.58% for the pristine, suggesting improved photocatalytic performance.