基于金属基选择性还原催化剂的光催化燃料电池废水深度处理研究

We still face serious challenge toward the safety of aquatic environment all over China nowadays. Many districts, especially these located in the regions near the big rivers, restricted higher discharging limit of COD and total nitrogen which is extreme challenge to traditional wastewater treatment. The energy cost is the key problem and a new advanced oxidation technology with energy benefit and low cost is absolutely an urgent demand. In this research, a new photocatalytic fuel cell for wastewater treatment was introduced, in which COD is efficiently oxidized by the exited photocatalysis holes with a simultaneously generation of current in the external circuit and a selective reduction of oxygen to hydrogen peroxide and nitrate to nitrogen. In this process, the “waste” chemical energy hidden in the organic compound of COD could be easily recycled with an oriented synthesis of reductive products with benefit and reusable electricity of external current, and therefore the whole cost of the treatment could be significantly reduced. The major focus of this research includes: i) high-efficient catalyst toward two electron reduction of oxygen to hydrogen peroxide with low resistance, wide applicable potential window, and high photocurrent. Binary and ternary metal based catalysts with nano structure to provide high surface area are preferentially focused. ii) reduction of nitrate with high selectivity to nitrogen with metal based catalyst. The operation potential and the optimizing of the catalyst are focused. iii) improving of the energy efficiency of the photocatalytic fuel cell under visible and ultraviolet light with different cathodic reactions, including the optimizing of the self-bias, e.g. using PV junction, with a priority aim of developing low cost photocatalytic fuel cell for advanced wastewater treatment.

目前，我国水环境形势严峻，沿江等COD、总氮排放标准一提再提，而满足上述标准对废水进行深度处理。现有的废水深度处理技术面临处理效果与能耗的矛盾，继续开发新的能源效益较高的低成本废水深度处理方法。本研究将光催化燃料电池用于废水深度处理， 利用光阳极降解COD产生的电子，同时在外电路产生电流并在阴极实现氧、氮的选择性还原，通过回收“废”化学能提高整体工艺的能效，降低处理成本。具体的研究包括：1）研究高效金属基氧选择性催化剂的制备方法及其复杂纳米结构的合成，研制具有高还原电流、宽选择性电位窗口的金属基二/三元化合物电极；2）研究氮选择性还原催化剂的开发及其电位控制，改进催化剂优化氮定向阴极还原；3）研究可见光/紫外辐照光催化燃料电池的全工艺能效与阴极匹配电位原理，优化不同阴极匹配的光催化燃料电池的自偏压设置，开发低能耗光催化燃料电池废水深度处理工艺。

目前，我国水环境形势严峻，沿江等COD、总氮排放标准一提再提，而满足上述标准对废水进行深度处理。现有的废水深度处理技术面临处理效果与能耗的矛盾，亟需开发新的能源效益较高的低成本废水深度处理方法。本研究将光催化燃料电池用于废水深度处理，利用光阳极降解COD产生的电子，同时在外电路产生电流并在阴极实现氧、氮的选择性还原，通过回收“废”化学能提高整体工艺的能效，降低处理成本。本项目将光催化燃料电池产生的电子用于阴极电催化在线生成过氧化氢，成功研发了具有纳米花结构的三维黄铁矿型二硫化钴催化剂（pyrite nano-CoS2）。证明了1D纳米线型CoS2不但具有较大的ORR-to-H2O2电流，其反应的选择也非常优异，性能甚至超过此前被认为是ORR-to-H2O2反应选择性最优异的贵金属Au；将阴极产生的电子用于氮还原反应。阐明了所制备的微生物电化学电极能在光催化燃料电池提供的0.25 V电压电压条件下驯化强化微生物脱氮，证明了电化学氮还原与微生物反硝化的耦合机制，而强化后Phyllobacterium菌及Caenispirillum菌群的提高是硝酸盐氮的反硝化性能提高的关键。在高效光阳极提供光生电子方面，分别采用超声辅助阳极氧化的方法成功制备了高效降解污染物能力的深丘型二氧化钛纳米管电极与具有高效电子利用率的1D结构的二氧化钛纳米线电极，后者能获得理论二氧化钛电极60%的光电流，具备高效的产电性能。在光催化电极反应器原理上，论证了其电流输出的电位匹配原理，证明了光催化电极反应器中电流输出受限于电位匹配，阐明了通过外置异质节提供偏压的方法有效打破电位匹配限制，发挥半导体应有的高性能，大幅提高产电输出，并能大幅提高污染物降解性能，从反应器原理角度提出了优化光催化燃料电池性能的解决方案。