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

Abstract

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.

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“…Localized electronic states are introduced into the forbidden gap by doping with cations, whereas the valence band is widened by doping with anions. [72] Morphology of the material is dependent on the synthesis method and choice of precursors which is ultimately an important factor in band engineering. [73] Because of its superior visible light harvesting, increased charge separation, layered structure equipped with high surface area, and optimal band structure for deep redox potential, heterojunction creation is also an excellent technique.…”

“…Band structure can be modified by doping it with anions or cations, which will increase the light‐driven charge carrier segregation and visible light absorption. Localized electronic states are introduced into the forbidden gap by doping with cations, whereas the valence band is widened by doping with anions [72] . Morphology of the material is dependent on the synthesis method and choice of precursors which is ultimately an important factor in band engineering [73] .…”