The effect of defects on electron–hole separation is not always clear and is sometimes contradictory. Herein, we initially built clear models of two-dimensional atomic layers with tunable defect concentrations, and hence directly disclose the defect type and distribution at atomic level. As a prototype, defective one-unit-cell ZnIn₂S₄ atomic layers are successfully synthesized for the first time. Aberration-corrected scanning transmission electron microscopy directly manifests their distinct zinc vacancy concentrations, confirmed by positron annihilation spectrometry and electron spin resonance analysis. Density-functional calculations reveal that the presence of zinc vacancies ensures higher charge density and efficient carrier transport, verified by ultrafast photogenerated electron transfer time of ∼15 ps from the conduction band of ZnIn₂S₄ to the trap states. Ultrafast transient absorption spectroscopy manifests the higher zinc vacancy concentration that allows for ∼1.7-fold increase in average recovery lifetime, confirmed by surface photovoltage spectroscopy and PL spectroscopy analysis, which ensures promoted carrier separation rates. As a result, the one-unit-cell ZnIn₂S₄ layers with rich zinc vacancies exhibit a carbon monoxide formation rate of 33.2 μmol g^–1 h^–1, roughly 3.6 times higher than that of the one-unit-cell ZnIn₂S₄ layers with poor zinc vacancies, while the former’s photocatalytic activity shows negligible loss after 24 h photocatalysis. This present work uncovers the role of defects in affecting electron–hole separation at atomic level, opening new opportunities for achieving highly efficient solar CO₂ reduction performances.

中文翻译：

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缺陷介导的单孔ZnIn ₂ S ₄层中的电子-孔分离，可增强太阳能驱动的CO ₂还原

缺陷对电子-空穴分离的影响并不总是清楚的，有时是矛盾的。在本文中，我们最初建立了具有可调缺陷浓度的二维原子层的清晰模型，因此直接公开了原子级的缺陷类型和分布。作为原型，有缺陷的单体电池ZnIn ₂ S ₄原子层首次成功合成。像差校正的扫描透射电子显微镜直接显示出它们独特的锌空位浓度，这通过正电子an没光谱法和电子自旋共振分析得以证实。密度泛函计算表明，锌空位的存在可确保更高的电荷密度和有效的载流子传输，这已由距ZnIn ₂ S ₄的导带约15 ps的超快光生电子转移时间验证陷阱状态。超快速瞬态吸收光谱法显示出较高的锌空位浓度，可使平均回收寿命增加约1.7倍，这已通过表面光电压光谱法和PL光谱法分析得到证实，这可确保提高的载流子分离率。结果，具有大量锌空位的单晶胞ZnIn ₂ S ₄层的一氧化碳形成速率为33.2μmolg ^–1 h ^–1，大约比单晶胞ZnIn _2的高3.6倍。小号₄层中锌空位较差，而前者的光催化活性在光催化24小时后显示损失可忽略不计。这项工作揭示了缺陷在原子水平上影响电子-空穴分离的作用，为实现高效的太阳能CO ₂还原性能开辟了新的机会。