Visualization of Electrochemically Accessible Sites in Flow-through Mode for Maximizing Available Active Area toward Superior Electrocatalytic Ammonia Oxidation,Environmental Science & Technology

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Visualization of Electrochemically Accessible Sites in Flow-through Mode for Maximizing Available Active Area toward Superior Electrocatalytic Ammonia Oxidation
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2022-06-23 , DOI: 10.1021/acs.est.2c01707
Yu Chen ₁ , Gong Zhang ₁ , Qinghua Ji ₁ , Huachun Lan ₁ , Huijuan Liu ₁ , Jiuhui Qu ₁

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Active chlorine species-mediated electrocatalytic oxidation is a promising strategy for ammonia removal in decentralized wastewater treatment. Flow-through electrodes (FTEs) provide an ideal platform for this strategy because of enhanced mass transport and sufficient electrochemically accessible sites. However, limited insight into spatial distribution of electrochemically accessible sites within FTEs inhibits the improvement of reactor efficiency and the reduction of FTE costs. Herein, a microfluidic-based electrochemical system is developed for the operando observation of microspatial reactions within pore channels, which reveals that reactions occur only in the surface layer of the electrode thickness. To further quantify the spatial distribution, finite element simulations demonstrate that over 75.0% of the current is accumulated in the 20.0% thickness of the electrode surface. Based on these findings, a gradient-coated method for the active layer was proposed and applied to a Ti/RuO₂ porous electrode with an optimized pore diameter of ∼25 μm, whose electrochemically accessible surface area was 381.7 times that of the planar electrode while alleviating bubble entrapment. The optimized reactor enables complete ammonia removal with an energy consumption of 60.4 kWh kg^–1 N, which was 24.2% and 39.9% less than those with pore diameters of ∼3 μm and ∼90 μm, respectively.

中文翻译：

流通模式下电化学可及位点的可视化，以最大限度地提高可用活性面积，实现卓越的电催化氨氧化

活性氯物种介导的电催化氧化是一种在分散式废水处理中去除氨的有前景的策略。流通电极 (FTE) 为这种策略提供了一个理想的平台，因为它增强了质量传输和足够的电化学可访问位点。然而，对 FTE 内电化学可及位点的空间分布的有限了解阻碍了反应器效率的提高和 FTE 成本的降低。在此，开发了一种基于微流体的电化学系统，用于操作观察孔隙通道内的微空间反应，这表明反应仅发生在电极厚度的表层。为了进一步量化空间分布，有限元模拟表明超过 75.0% 的电流累积在电极表面的 20.0% 厚度中。基于这些发现，提出了一种活性层的梯度涂覆方法，并将其应用于Ti/RuO ₂多孔电极，优化孔径为~25 μm，其电化学可及表面积是平面电极的381.7倍，而减轻气泡的束缚。^{优化后的反应器能够以 60.4 kWh kg –1}的能耗完全去除氨N，分别比孔径为~3μm和~90μm的那些小24.2％和39.9％。

更新日期：2022-06-23

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