Photoinduced Surface Electric Fields and Surface Population Dynamics of GaP(100) Photoelectrodes
Photoinduced Surface Electric Fields and Surface Population Dynamics of GaP(100) Photoelectrodes
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DOI：
10.1021/acs.jpcc.2c01806
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Tong Zhang;Zhi-Chao Huang-Fu;Yuqin Qian;Hong-jie Gao;Jesse B. Brown;Y. Rao
中科院分区：
文献类型：
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作者：
Tong Zhang;Zhi-Chao Huang-Fu;Yuqin Qian;Hong-jie Gao;Jesse B. Brown;Y. Rao
磷化镓（GaP）光电极因其在CO2还原反应中的催化和光电催化作用而受到广泛关注。了解光电极表面的动力学机制对于提高光电极在任何应用中的工作效率都是至关重要的。然而，这些材料的光致表面动力学的知识是缺乏的。本文利用时间分辨电子和频产生技术（TR-ESFG）研究了n型和p型GaP（100）半导体的表面动力学。瞬态ESFG谱表明，n型和p型GaP（100）的四个表面态都参与了后续的动力学过程。表面态的瞬态光谱特征表明，对于p型GaP，光激发电子向表面区域移动，而对于n型GaP，光激发空穴向表面区域移动.这些载流子首先建立表面电场，导致与能量密度相关的能带平坦化。表面电场的建立速率为2.86 ± 0.30 ps ~（-1）（n型）和2.50 ± 0.25 ps ~（-1）（p型）。随后，一个相对缓慢的过程发生，归因于人口动态的表面状态依赖于应用的能量密度。发现表面布居是一个双分子过程，n型GaP的布居速率为0.020 ± 0.002cm ~ 2s ~（-1），p型GaP的布居速率为0.035 ± 0.002cm ~ 2s ~（-1）。与以前的假设相反，发现四种表面态，浅的和深的n型和p型GaP（100），都涉及表面电场和表面载流子布居。我们的时间分辨的表面特定的方法提供了独特的信息在环境条件下的光电极的表面动力学行为。
Gallium phosphide (GaP) photoelectrodes have received remarkable focus due to their applications in photocatalysis and photoelectrocatalysis of CO2reduction reactions. Understanding the dynamical mechanisms of surfaces of photoelectrodes is essential in improving their working efficiencies in any application. However, knowledge of photoinduced surface dynamics of these materials is lacking. Here, we investigate surface dynamics ofn-type andp-type GaP(100) semiconductors by utilizing time-resolved electronic sum frequency generation (TR-ESFG). Transient ESFG spectra showed that four surface states in bothn- andp-type GaP(100) were involved in subsequent kinetics. Transient spectral signatures of the surface states showed that photoexcited electrons move toward the surface regions forp-type GaP, while photoexcited holes move to the surface regions forn-type GaP. These carriers first build up surface electric fields, resulting in fluence-dependent band flattening. The buildup rates of the surface electric fields were found to be on the order of 2.86 ± 0.30 ps–1forn-type and 2.50 ± 0.25 ps–1forp-type. Subsequently, a relatively slow process occurs, being attributed to population dynamics of surface states dependent upon applied fluences. We found that surface population behaves as a bimolecular process with rates of 0.020 ± 0.002 cm2s–1forn-type and 0.035 ± 0.002 cm2s–1forp-type GaP. The four surface states, shallow and deep for bothn- andp-type GaP(100), were found to be involved in both surface electric fields and surface carrier populations, contrary to previous hypotheses. Our time-resolved surface-specific approach provides unique information on surface dynamical behaviors of photoelectrodes under ambient conditions.