This study presents a paired photoelectrochemical (PEC) system using dual photoelectrodes designed for comprehensive total nitrogen (TN) removal by converting NO₃^⁻ into non-toxic N₂ gas. Utilizing spaced TiO₂ nanotube arrays (STNA) optimized for precise metallic site engineering, bimetallic Pd-Cu and RuO₂ catalysts were tailored onto the STNA for the photocathode and photoanode, respectively. This configuration enabled the selective reduction of NO₃^⁻ to NH₃ at the photocathode, while the NH₃ was simultaneously oxidized to N₂ via reactive chlorine species (RCS) generated under light illumination. The paired PEC system achieved a TN removal efficiency of over 99.2% over eight cycles, totaling 32 hours of continuous operation without metal leaching and by-products formation. Even in complex real wastewater matrices, the paired photoelectrode system maintained a TN removal efficiency of 96.3%, demonstrating consistent performance in practical applications. Furthermore, the system exhibited a specific electric energy consumption (SEEC) approximately 7 times lower than conventional electrochemical (EC) systems, indicating improvements in cost-effectiveness and energy efficiency. This study establishes a foundation for advancing PEC systems in nitrogen removal and provides insights into the application of tailored metallic site engineering on photoelectrodes for environmental applications.

中文翻译：

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配对光电化学系统，用于通过间隔 TiO2 纳米管平台中的工程活性位点去除总氮

本研究提出了一种使用双光电电极的配对光电化学 （PEC） 系统，该系统旨在通过将 NO ₃ ^⁻ 转化为无毒的 N ₂ 气体来全面去除总氮 （TN）。利用针对精确金属位点工程优化的间隔 TiO ₂ 纳米管阵列 （STNA），在 STNA 上分别为光阴极面和光阳极定制了双金属 Pd-Cu 和 RuO ₂ 催化剂。这种配置能够在光电阴极面上选择性地将 NO ₃ 还原为 NH ₃ ，同时通过在光照射下产生的活性氯 （RCS） 将 NH ₃ 同时氧化为 N ₂ ^⁻ 。配对的 PEC 系统在 8 个循环中实现了超过 99.2% 的 TN 去除效率，总共连续运行了 32 小时，没有金属浸出和副产物形成。即使在复杂的实际废水基质中，配对的光电电极系统也保持了 96.3% 的 TN 去除效率，在实际应用中表现出一致的性能。此外，该系统的比电能消耗 （SEEC） 比传统电化学 （EC） 系统低约 7 倍，表明成本效益和能源效率有所提高。本研究为推进 PEC 系统脱氮奠定了基础，并为定制金属现场工程在光电电极上的环境应用提供了见解。