Engineering waveguide surface by gradient etching for uniform light scattering in photocatalytic applications
Engineering waveguide surface by gradient etching for uniform light scattering in photocatalytic applications
复制标题
通过梯度蚀刻工程波导表面，以实现光催化应用中的均匀光散射
DOI：
10.1016/j.ceja.2021.100192
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发表时间：
2021
影响因子：
--
通讯作者：
Erickson, David
中科院分区：
文献类型：
--
作者：
Elvis Cao, Xiangkun;Hong, Tao;Hong, Spencer;Erickson, David
在光反应器中，不均匀的光分布导致区域要么光线过多，要么光线照射不足。将波导等光导元件集成到光催化反应器中已成为改善光传输的新兴方法。然而，具有恒定表面特性的传统波导在侧面照射下散射光强度呈指数衰减。这减少了光传播长度并阻碍了按比例放大的潜力。在这项工作中，我们推导了衰减系数与蚀刻时间之间的关系，确定了均匀散射的蚀刻时间和波导位置之间的相关性，并通过设计波导的表面粗糙度分布来实验验证不同的光散射剖面。我们应用无量纲数（变异系数）来表征梯度蚀刻、均匀蚀刻和未修改波导的相对光分布均匀性。通过梯度蚀刻的散射光均匀性比均匀蚀刻高13倍以上。此外，梯度蚀刻的光分布比其他方法（例如尖端涂层、物理雕刻和工程柱）表现出更好的均匀性。然后，我们在亚甲基蓝光降解测试中评估了不同光散射分布对光催化活性的影响，其中未蚀刻、均匀蚀刻和梯度蚀刻波导用作内部光导元件。梯度蚀刻波导的光降解活性比均匀蚀刻设计提高约 4 倍，比非蚀刻配置提高约 8 倍。这一结果强调了波导的梯度蚀刻作为精确光传输以提高光分布均匀性的可行方法，从而提高光催化反应器的反应速率。
In photoreactors, non-uniform light distribution leads to regions either with an overabundance of light or insufficient light irradiation. The integration of light-guiding elements such as waveguides into photocatalytic reactors has been an emerging approach to improve light delivery. However, traditional waveguides with constant surface properties experience an exponential decay in scattering light intensity under side irradiation. This reduces the light propagation length and hinders the scale-up potential. In this work, we derive the relationship between attenuation coefficients with etching time, determine the correlation between etching time and waveguide location for uniform scattering, and experimentally validate different light scattering profiles by engineering the surface roughness distribution of waveguides. We apply a dimensionless number, the coefficient of variation, to characterize the relative light distribution uniformity for gradient-etched, uniform-etched, and unmodified waveguides. Scattering light uniformity via gradient etching is more than 13 times higher than that for uniform-etching. In addition, the light distribution for gradient etching exhibits improved uniformity than other approaches, such as tip coating, physical carving, and engineered pillars. We then evaluate the effect of different light scattering profiles on photocatalytic activities in a photodegradation test for methylene blue, with non-etched, uniform-etched, and gradient-etched waveguides serving as internal light-guiding elements. Gradient-etched waveguides show ∼4 times improvement in photodegradation activity over uniform-etched designs and ∼8 times over non-etched configurations. This result underscores gradient etching for waveguides as a viable approach for precision light delivery to increase the light distribution uniformity, thus enhancing reaction rates for photocatalytic reactors.
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