ZnO monolayer possesses band structure matching the conditions of water splitting for hydrogen generation but cannot well response to the visible light, while CdO one, contrariwise, have obvious optical absorption in the visible light range but no satisfactory band edges for the water splitting to produce hydrogen. Here, we predict a two-dimensional ZnCdO2 structure comprising of ZnO and CdO ones to achieve their strengths. The band structures, optical properties, carrier mobility, and the strain engineering for ZnCdO2, ZnO and CdO monolayers are investigated by using the first-principles hybridization functional calculations. The results demonstrate that the two-dimensional ZnCdO2 structure is a promising candidate for water splitting to produce hydrogen. All the structures show a direct band energy gap and the character remains unchanged under the considered biaxial strains. All the conduction band minimums are suitable for water splitting reaction even under the -4% to +4% strain. Moreover, the valence band maximum of ZnCdO2 monolayer matches the conditions of the water-splitting reaction under the -2% to +4% strain. Interestingly, the unsatisfactory valence band maximum of CdO monolayer can be overcome by strain larger than +2%. As expected, the enhanced optical absorption in the visible light range is observed for the ZnCdO2 monolayer. Additionally, the mobilities of the hole and the electron are significantly different for the three monolayers, implying that the low recombination ratio of the photogenerated carrier pairs is available, which is also beneficial for the photocatalytic performance. Therefore, ZnCdO2 monolayer and CdO monolayer (with tensile strain larger than 2%) is a promising candidate for the water splitting to produce hydrogen under the irradiation of the solar light.

中文翻译：

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ZnCdO2单层-ZnO和CdO单层的复杂2D结构，用于可见光驱动的光催化水分解。

ZnO单层具有与水分解产生氢的条件相匹配的能带结构，但不能很好地响应可见光，而CdO一反之，在可见光范围内具有明显的光吸收，但是没有令人满意的能带边缘使水分解产生氢。在这里，我们预测由ZnO和CdO组成的二维ZnCdO2结构，以实现其强度。通过第一性原理杂交函数计算研究了ZnCdO2，ZnO和CdO单层的能带结构，光学性质，载流子迁移率和应变工程。结果表明，二维ZnCdO2结构是水分解产生氢的有希望的候选物。所有结构都显示出直接的能带隙，并且在所考虑的双轴应变下其特性保持不变。所有的导带最小值都适用于水分解反应，即使在-4％至+ 4％应变下也是如此。此外，ZnCdO2单层的价带最大值与在-2％至+ 4％应变下水分解反应的条件相匹配。有趣的是，大于+ 2％的应变可以克服CdO单层的价带最大峰。如所预期的，对于ZnCdO 2单层在可见光范围内观察到增强的光吸收。此外，三个单层的空穴和电子的迁移率显着不同，这意味着可以利用光生载流子对的低重组率，这也有利于光催化性能。因此，ZnCdO2单层和CdO单层（拉伸应变大于2％）是在太阳光照射下水分解产生氢的有希望的候选物。