Urine is the main source of nitrogen pollution, while urea is a hydrogen-enriched carrier that has been ignored. Decomposition of urea to H₂ and N₂ is of great significance. Unfortunately, direct urea oxidation suffers from sluggish kinetics, and needs strong alkaline condition. Herein, we developed a self-driving nano photoelectrocatalytic (PEC) system to efficiently produce hydrogen and remove total nitrogen (TN) for urine treatment under neutral pH conditions. TiO₂/WO₃ nanosheets were used as photoanode to generate chlorine radicals (Cl•) to convert urea-nitrogen to N₂, which can promote hydrogen generation, due to the kinetic advantage of Cl^–/Cl• cyclic catalysis. Copper nanowire electrodes (Cu NWs/CF) were employed as the cathode to produce hydrogen and simultaneously eliminate the over-oxidized nitrate-nitrogen. The self-driving was achieved based on a self-bias photoanode, consisting of confronted TiO₂/WO₃ nanosheets and a rear Si photovoltaic cell (Si PVC). The experiment results showed that hydrogen generation with Cl• is 2.03 times higher than in urine treatment without Cl•, generating hydrogen at 66.71 μmol h⁻¹. At the same time, this system achieved a decomposition rate of 98.33% for urea in 2 h, with a reaction rate constant of 0.0359 min⁻¹. The removal rate of total nitrogen and total organic carbon (TOC) reached 75.3% and 48.4% in 2 h, respectively. This study proposes an efficient and potential urine treatment and energy recovery method in neutral solution.

中文翻译：

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基于自驱动纳米光电催化系统的中性溶液中尿液高效制氢和总氮去除


尿液是氮污染的主要来源，而尿素则是一种被忽视的富氢载体。尿素分解为H ₂和N ₂具有重要意义。不幸的是，直接尿素氧化动力学缓慢，并且需要强碱性条件。在此，我们开发了一种自驱动纳米光电催化（PEC）系统，可在中性pH条件下高效产生氢气并去除总氮（TN），用于尿液处理。由于Cl ^– /Cl•循环催化的动力学优势，TiO ₂ /WO ₃纳米片被用作光阳极，产生氯自由基(Cl•)，将尿素氮转化为N ₂ ，从而促进氢气的产生。采用铜纳米线电极（Cu NWs/CF）作为阴极产生氢气，同时消除过度氧化的硝态氮。自驱动是基于自偏置光电阳极实现的，该光电阳极由相对的TiO ₂ /WO ₃纳米片和后部硅光伏电池（Si PVC）组成。实验结果表明，使用Cl•处理的氢气产生量比不使用Cl•的尿液处理高2.03倍，产生66.71 μmol h ^-1的氢气。同时，该体系在2 h内实现了尿素98.33%的分解率，反应速率常数为0.0359 min ^-1 。 2 h内总氮和总有机碳（TOC）去除率分别达到75.3%和48.4%。本研究提出了一种高效且有潜力的中性溶液尿液处理和能量回收方法。