In Silico Band-Gap Engineering of Cr₂C MXenes as Efficient Photocatalysts for Water-Splitting Reactions

Hydrogen is a significantly advantageous clean and sustainable energy carrier over other energy sources. Therefore, hydrogen production using water-splitting technology is a promising strategy as a clean source of energy. In this work, we computationally explored the effect of different surface functionalization on the structural, electronic, and optical properties of Cr2CT2 MXenes (T = F, Cl, H, and OH) for water-splitting applications. The pure functionalization resulted in antiferromagnetic (AFM) spin-unpolarized MXenes, while the mixed functionalization induced asymmetric AFM semiconductor formation. A tunable band gap size is achievable under different functionalization of Cr2CT2 MXenes. Most of the functionalized Cr2CT2 MXenes display band gaps in the visible range with band edge alignment appropriate for water-splitting reactions. In addition, an indirect band gap characteristic is observed for some of the functionalized MXenes, which is beneficial for the spatial charge pair separation and migration. The results presented herein enrich our understanding of the optoelectronic properties of potential functionalized MXenes as photocatalysts for water-splitting reactions and inspire experimentalists to find the suitable MXene candidate for such applications.