Guo Weiyan, Guo Yating, Dong Hao, Zhou Xin
Institute of Chemistry for Functionalized Materials, School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, Liaoning 116029, China.
Phys Chem Chem Phys. 2015 Feb 28;17(8):5817-25. doi: 10.1039/c4cp05637j.
A systematic study using density functional theory has been performed for β-Ga2O3 doped with non-metal elements X (X = C, N, F, Si, P, S, Cl, Se, Br, and I) to evaluate the effect of doping on the band edges and photocatalytic activity of β-Ga2O3. The utilization of a more reliable hybrid density functional, as prescribed by Heyd, Scuseria and Ernzerhof, is found to be effective in predicting the band gap of β-Ga2O3 (4.5 eV), in agreement with the experimental result (4.59 eV). Based on the relaxed structures of X-doped systems, the defect formation energies and the plots of density of states have been calculated to analyze the band edges, the band gap states and the preferred doping sites. Our results show that the doping is energetically favored under Ga-rich growth conditions with respect to O-rich growth conditions. It is easier to replace the threefold coordinated O atom with non-metal elements compared to the fourfold coordinated O atom. X-doped systems (X = C, Si, P) show no change in the band gap, with the presence of discrete midgap states, which have adverse effect on the photocatalytic properties. The photocatalytic redox ability can be improved to a certain extent by doping with N, S, Cl, Se, Br, and I. The band alignments for Se-doped and I-doped β-Ga2O3 are well positioned for the feasibility of both photo-oxidation and photo-reduction of water, which are promising photocatalysts for water splitting in the visible region.
利用密度泛函理论对掺杂非金属元素X（X = C、N、F、Si、P、S、Cl、Se、Br和I）的β-Ga2O3进行了系统研究，以评估掺杂对β-Ga2O3能带边缘和光催化活性的影响。结果发现，采用Heyd、Scuseria和Ernzerhof规定的更可靠的杂化密度泛函，能够有效地预测β-Ga2O3的带隙（4.5 eV），与实验结果（4.59 eV）一致。基于X掺杂体系的弛豫结构，计算了缺陷形成能和态密度图，以分析能带边缘、带隙态和优先掺杂位点。我们的结果表明，相对于富氧生长条件，在富镓生长条件下，掺杂在能量上更有利。与四重配位的O原子相比，用非金属元素取代三重配位的O原子更容易。X掺杂体系（X = C、Si、P）的带隙没有变化，但存在离散的中间带隙态，这对光催化性能有不利影响。通过掺杂N、S、Cl、Se、Br和I，光催化氧化还原能力可以在一定程度上得到提高。硒掺杂和碘掺杂的β-Ga2O3的能带排列有利于水的光氧化和光还原，是可见光区域有前景的光催化水分解催化剂。
