Broad-pH-value photocatalyst of Janus MXene monolayers functionalized with group VIA elements

Based on first-principles calculations, we conducted a systematic investigation into the photocatalytic performance of Janus MXene Y2COX (X = O, S, Se) monolayers. Our findings reveal that Y2COX monolayers exhibit exceptional photocatalytic overall water splitting capabilities. Benefiting from the asymmetry of the Janus structure and the differences in surface-terminated atoms, Y2COS and Y2COSe monolayers generate built-in electric fields (Eint) as high as 8.7 × 109 and 8.4 × 109 V/m, respectively, significantly promoting the effective separation of photogenerated electron–hole pairs. Additionally, Y2COX monolayers possess wide bandgaps and high electrostatic potential differences (ΔΦ), enabling efficient photocatalytic water splitting across a broad pH range (pH = 0–14). Furthermore, these monolayers exhibit outstanding optical absorption properties in the visible region, with a maximum absorption coefficient of up to 7.12 × 105 cm−1. This study provides important theoretical insights for developing photocatalytic overall water splitting materials with wide pH adaptability.