NO₃^– is an undesirable environmental pollutant that causes eutrophication in aquatic ecosystems, and its pollution is difficult to eliminate because it is easily converted into NH₄⁺ instead of N₂. Additionally, it is a high-energy substance. Herein, we propose a novel denitrification fuel cell to realize the chemical energy recovery of NO₃^– and simultaneous conversion of total nitrogen (TN) into N₂ based on the outstanding ability of NH₄⁺ generation on a three-dimensional copper nanowire (CNW)-modified copper foam (CF) cathode (CNW@CF). The basic steps are as follows: direct and highly selective reduction of NO₃^– to NH₄⁺ rather than to N₂ on the CNW@CF cathode, on which negative NO₃^– ions can be easily adsorbed due to their double-electron layer structure and active hydrogen ([H]) can be generated due to a large number of catalytic active sites exposed on CNWs. Then, NH₄⁺ is selectively oxidized to N₂ by the strong oxidation of chlorine free radicals (Cl^•), which originate from the reaction of chlorine ions (Cl^–) by photogenerated holes (h⁺) and hydroxyl radicals (OH^•) under irradiation. Then, the electrons from the oxidation on the photoanode is transferred to the cathode to form a closed loop for external power generation. Owing to the continuous redox loop, NO₃^– completely reduces to N₂, and the released chemical energy is converted into electrical energy. The results indicate that 99.9% of NO₃^– can be removed in 90 min, and the highest yield of electrical power density reaches 0.973 mW cm^–2, of which the nitrate reduction rates on the CNW@CF cathode is 79 and 71 times higher than those on the Pt and CF cathodes, respectively. This study presents a novel and robust energy recycling concept for treating nitrate-rich wastewater.

中文翻译：

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新型反硝化燃料电池，用于在 CNW@CF 阴极上产生 NH4+ 的硝酸盐-N 和 TN 去除能量回收

NO ₃ ^–是一种不良的环境污染物，会导致水生生态系统富营养化，其污染难以消除，因为它很容易转化为NH ₄ ⁺而不是N ₂。此外，它是一种高能物质。在此，我们基于三维铜纳米线 (CNW )上出色的 NH ₄ ⁺生成能力，提出了一种新型反硝化燃料电池，可实现 NO ₃ ^-的化学能回收和总氮 (TN) 向 N ₂的同时转化。 )-改性泡沫铜 (CF) 阴极 (CNW@CF)。基本步骤如下： NO _{3的直接和高选择性还原}^–在 CNW@CF 阴极上转变为 NH ₄ ⁺而不是 N ₂，负 NO ₃ ^–离子由于其双电子层结构很容易吸附在其上，并且由于大量的催化活性位点暴露在 CNWs 上。然后，NH ₄ ⁺被氯自由基（Cl • ）的强氧化选择性氧化为N ₂，氯自由基（Cl ^{• ）}来源于光生空穴（h ⁺）和羟基自由基（OH ^•) 在辐照下。然后，来自光阳极上的氧化作用的电子被转移到阴极，形成一个外部发电的闭环。由于连续的氧化还原循环，NO ₃ ^-完全还原为N ₂，释放的化学能转化为电能。结果表明，90 min内可去除99.9%的NO ₃ ^-，电功率密度最高产率为0.973 mW cm ^-2，其中CNW@CF正极的硝酸盐还原率分别高出79倍和71倍分别比 Pt 和 CF 阴极上的那些。本研究提出了一种用于处理富含硝酸盐的废水的新颖而强大的能量回收概念。