Engineering Electronic Structure and Band Alignment of 2D Mg(OH)₂ via Anion Doping for Photocatalytic Applications

The wide bandgap of 2D Mg(OH)₂ inhibits its applications in visible-light photocatalytic applications. Besides, its mismatched band alignment to the redox potential of O₂/H₂O, brings about low efficacy of water-splitting performance. Therefore, to release the powder of 2D Mg(OH)₂ in photocatalytic research, we explore anion doping strategies to engineer its electronic structure. Here, anion doping effects on electronic properties of 2D Mg(OH)₂ are investigated by using DFT calculations for seven dopants (F, Cl, S, N, P, SO₄, and PO₄). We found (1) S, N and P doping remarkably reduces its band gap from 4.82 eV to 3.86 eV, 3.79 eV and 2.69 eV, respectively; (2) the band gap reduction is induced by the electron transfer to the dopant atoms; (3) F, Cl, SO₄, and PO₄ doping shifts its valence band to be lower than the oxidation potential of O₂/H₂O to render its band structure appropriate for photocatalytic water splitting. These results suggest that not only electrical conductivity of 2D Mg(OH)₂ can be increased but also their band structure be aligned by using the proposed anion doping strategy. These results enable a new photocatalytic materials design approach while offering exciting possibilities in applications of high-current electrolysis, chemical gas sensing, and photocatalysis.