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.
Highlights
Available and non-toxic Mg(OH)2 represents a fine example of multifunctional compounds with extensive technological and industrial applications [1], such as removing pollutants using its adsorptive and coagulative properties [2,3,4,5,6], acting as an effective antibacterial agent [7], protecting paper by reducing the paper ageing [8], adding as a component in organic-inorganic composite membrane [9,10], utilizing as a new-generation flame retardant and smoke suppression [11,12]
Doping is a useful tool for the modulation of the electronic structure of semiconductors
Since the bandgap region of the electronic structure of 2D Mg(OH)2 is predominantly controlled by the O-2p electrons, anion doping may make direct contribution to the valence band top or conduction band bottom depending on their electronegativity, which will explicitly affect the bandgap and the band alignment
Summary
Available and non-toxic Mg(OH) represents a fine example of multifunctional compounds with extensive technological and industrial applications [1], such as removing pollutants using its adsorptive and coagulative properties [2,3,4,5,6], acting as an effective antibacterial agent [7], protecting paper by reducing the paper ageing [8], adding as a component in organic-inorganic composite membrane [9,10], utilizing as a new-generation flame retardant and smoke suppression [11,12]. Owing to different deposition and processing methods as well as characterization tools, Mg(OH) reports a scattered experimental band gap values from 5.17 eV [17,18], 5.47 eV [19], 5.70 eV [17], to 7.60 eV [20], and is considered a wide gap insulator. It is used as a buffer layer in heterostructure solar cells [18,21] and to suppress recombination of photogenerated electrons in dye-sensitized solar cells [22,23]. Cobalt doping is examined to tune the bandgap of Mg(OH) , and 10% Co-doping slightly narrows the band gap from 5.47 eV of pure
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