【作者】 李林森；

【导师】 周保学；

【作者基本信息】 上海交通大学 ， 环境科学与工程， 2020， 博士

【摘要】 利用太阳能光电催化体系实现有机物降解产能或水分解产氢具有良好的应用前景。然而,现有光电催化体系受限于电极电荷传输效率和体系反应效率较差,导致有机物降解及分解水产氢效率仍然较低。论文首先从光阳极材料空穴传输与利用效率着手,通过在BiVO₄表面修饰连续空穴传输层,并考查不同传输层对光电催化性能影响,分别制备了可以用于有机物降解和分解水产氢的BiVO₄电极材料,并基于此发展了自驱动光电催化体系;基于制备的BiVO₄及相关电极材料,通过强化体系链式自由基反应效率以及利用阴极产双氧水（H₂O₂）、使用助催化剂二硫化钨（WS₂）等,发展了一系列新的自驱动光催化废水燃料电池（PFC）体系,提升了难降解有机污染物降解与产电的效率,并克服了现有PFC体系过度依赖体系低pH等问题。主要内容如下:1.BiVO₄光阳极的修饰与光电催化性能。基于BiVO₄光阳极电荷传输性能较差和表面水氧化活性较低的问题,提出通过修饰连续空穴传输层来提升BiVO₄空穴利用效率从而改善BiVO₄光电化学性能的新思路。利用旋涂法在BiVO₄表面修饰Fe₂O₃作为体相空穴传输层提升BiVO₄体相空穴传输效率,成功制备了高效稳定的Fe₂O₃/BiVO₄电极,该电极用于有机物降解表现出了良好的稳定性和光电催化降解有机物性能,180 min的COD去除率达到80.0%,是纯BiVO₄光阳极的有2.09倍;在此基础上,进一步修饰双层NiOOH/FeOOH作为表面空穴传输层降低析氧过电位,提升空穴氧化水的效率,得到了具有优异光电分解水产氢性能的NiOOH/FeOOH/Fe₂O₃/BiVO₄电极,在1.23 V vs.RHE,光电流达到了2.24 mA/cm²,是纯BiVO₄电极的2.95倍;最后,将硅太阳能光伏电池（SiPVC）与NiOOH/FeOOH/Fe₂O₃/BiVO₄电极组装在一起构建了串联PEC体系用于自驱动水分解产氢,其光电流达到了～2.60 mA/cm²,对应的太阳能氢气转换效率（STH）达到了3.2%。2.自驱动光催化废水燃料电池体系的构建。将具有良好有机物降解性能的Fe₂O₃/BiVO₄和SiPVC组成自偏压复合光阳极,并以Pt黑为阴极构建了自驱动光催化废水燃料电池体系,强化体系中羟基（HO·）和超氧自由基（O₂·^-）降解有机物和发电的效率。在此基础上,通过引入亚铁离子(Fe²⁺)和四聚磷酸盐（TPP）的络合物,构建了具有链式自由基反应的自驱动光催化废水燃料电池体系,该体系可以在中性条件下稳定运行,HO·和O₂·^-的浓度得到了进一步提升,分别增加了7.28倍和7.99倍。与此同时,体系有机物降解和产电性能也得到了明显提升。亚甲基蓝的反应速率常数（k）提升了5.52倍,体系的短路电流(J_sc)和最大功率密度(JV_max)分别提升了8.05和11.67倍。此外,通过进一步研究了刚果红,甲基橙和苯酚的降解性能,发现k值同样提升了4.54-5.65倍。该自驱动光催化废水燃料电池体系还解决了链式自由基反应必须在酸性条件下运行的问题。3.阴极产H₂O₂协同强化自驱动光催化废水燃料电池性能。传统Pt黑阴极用于PFC体系时,大量电子还原质子产氢而造成电子浪费。基于此,论文将具有原位产H₂O₂的石墨毡（GF）材料作为PFC的阴极代替Pt黑,协同强化自驱动光催化废水燃料电池性能。通过在GF材料表面引入含氧官能团作为表面活性位点,强化GF表面2电子还原O₂过程,制备了高效产H₂O₂的活性GF阴极。活性GF的峰值电流由原始GF的0.40 mA/cm²提升到1.25 mA/cm²,产H₂O₂的法拉第效率从20.01%显著提高到74.09%。基于此阴极构建了自驱动光催化废水燃料电池体系,体系的JV_max和k是传统Pt黑阴极体系的2.69倍和5.15倍。进一步研究表明,体系H₂O₂浓度提升了24.13倍,O₂·^-和HO·浓度分别提升了1.87和1.48倍,达到了23.98×10^-5 mol/L和13.00×10^-4 mol/L。该研究表明,阴极产H₂O₂能协同强化自驱动光催化废水燃料电池性能。4.助催化剂强化自驱动光催化废水燃料电池的性能。在早期研究中,引入Fe²⁺/Fe³⁺循环催化的链式自由基反应能够明显提升光催化废水燃料电池的性能。尽管如此,电池的性能却受制于Fe²⁺/Fe³⁺的循环效率,特别是受制于Fe³⁺还原为Fe²⁺的低效率。基于该问题,本研究通过引入二硫化钨（WS₂）助催化剂,构建了WS₂助催化剂强化的自驱动光催化废水燃料电池体系。在WS₂助催化剂中,暴露的W⁴⁺具有还原Fe³⁺的能力,可以显著提高体系的Fe²⁺浓度,从而提升了Fe³⁺还原为Fe²⁺的效率,因而强化了HO·和O₂·^-的生成。实验结果表明,加入WS₂后HO·和O₂·^-分别提高了151%(6.89×10^-5 mol/L)和45%(3.31×10^-5 mol/L);当以GF为阴极时提供H₂O₂时,构建的电池体系中HO·和O₂·^-浓度分别提升了204%(8.32×10^-5 mol/L)和242%(7.79×10^-5 mol/L),而k值也提升了122%。此外,助催化剂WS₂的引入同时拓宽了体系运行的pH,体系在pH 2-9范围内均表现出高效的降解效率。本研究表明,助催化剂WS₂可以明显提升光催化废水燃料电池体系降解有机物和产电的性能。更多还原

【Abstract】 The utilization of solar photocatalytic system to achieve wastewater treatment and water splitting has a broad application prospect.However,the degradation efficiency of organic matter and hydrogen production efficiency from water in the photocatalytic system is still low due to the poor charge transfer efficiency of electrodes and the inadequate system design.Starting from the hole transport and utilization efficiency of photoanode material,the serial hole transfer layers were modified on the surface of bismuth vanadate（BiVO₄）and we got two BiVO₄ materials which could be used for organic degradation and water splitting,respectively.In addition,a tandem photoelectrochemistry（PEC）system was also developed to realize self-driven water splitting.Based on the prepared BiVO₄ and related electrode materials,a series of self-driven photocatalytic fuel cell（PFC）has been developed by enhancing the radical-chain reaction,using GF cathode to produce hydrogen peroxide（H₂O₂）,and introducing the cocatalyst of WS₂.At last,the efficient degradation and electricity generation of refractory organic pollutants were realized and the problem of over-dependence on low pH of existing PFC systems was overcome.The main contents are as follows:1.Modification and photocatalytic performance of BiVO4 photoanode.Based on the problems of poor charge transfer and surface water oxidation activity of BiVO₄,a new idea was proposed to improve the hole utilization efficiency and PEC performance of BiVO₄by modifying serial hole transfer layer.First,a Fe₂O₃/BiVO₄ electrode was successfully prepared by spin-coating hole transfer layer of Fe₂O₃ on the surface of BiVO₄ to promote the bulk hole transfer.The Fe₂O₃/BiVO₄ electrode exhibited good stability and photocatalytic performance for organic degradation,and the COD removal efficiency at 180min reached 80.0%,which was 2.09 times that of BiVO₄.On this basis,the double-layer NiOOH/FeOOH was modified as the surface hole transfer layer to reduce oxygen evolution overpotential and improve the efficiency of hole oxidation of water,and the NiOOH/FeOOH/Fe₂O₃/BiVO₄ electrode with higher hydrogen generation performance was obtained,which had the photocurrent of 2.24 mA/cm² at 1.23 V vs.RHE,about 2.95 times that of pristine BiVO₄ photoanode.Finally,the NiOOH/FeOOH/Fe₂O₃/BiVO₄ and SiPVC（photovoltaic cell）were assembled together to construct a tandem PEC system for self-driven hydrogen production from water.The photocurrent in the PEC system reached up to～2.60 mA/cm² and the corresponding solar-to-hydrogen conversion efficiency（STH）reached to 3.2%.2.Construction of radical-chain reaction in self-driven PFC system.A self-driven PFC system was constructed with a Pt black cathode and a composite electrode of Fe₂O₃/BiVO₄ photoanode and SiPVC for neutral organic wastewater degradation.On this basis,the hydroxyl radical（HO·）and superoxide radical（O₂·^-）in the PFC system were strengthened to improve organic pollutants oxidation and chemical energy conversion.By introducing Fe²⁺and tetrapolyphosphate（TPP）,which would form stable Fe²⁺complex in neutral solution,the self-driven PFC system with radical-chain reaction was constructed.The system could operate stably under neutral conditions,in which the HO·and O₂·^-concentration were further increased by 7.28 times and 7.99 times than traditional PFC,respectively.Furthermore,the degradation rate constant（k）is remarkably increased by 5.52times when methylene blue is used as a model pollutant.Meanwhile,the short-circuit current density(J_sc)and maximum power density(JV_max)have been increased by a factor of 8.05and 11.67 times in the same experiment,respectively.In addition,the degradation performance of Congo red,methyl orange and phenol was further studied,the k values were increased by 4.54-5.65 times.It was worth mentioning that the radical-chain reaction PFC system also solves the problem that traditional radical-chain reaction must operate under acidic condition.3.Synergistically improved performance of the self-driven PFC system by H2O2producing at GF cathode.When traditional Pt black was used as cathode in PFC system,a large number of electron was wasted to produce H₂.Based on this,the graphite felt（GF）material with in-situ H₂O₂ generation was used as the PFC cathode instead of Pt black to synergistically enhance the self-driven PFC performance.This GF cathode was activated by H₂SO₄ treatment to introduce oxygen-containing functional groups on its surface as surface-active sites and facilitate the two-electron pathway of H₂O₂ production.Remarkably,the peak current density of the activated GF cathode（-1.25 mA/cm²）was more than thrice that of the original GF cathode（-0.40 mA/cm²）,and its Faradaic efficiency significantly improved from 20.01%to 74.09%.The PFC equipped with the activated GF cathode harvested 2.69 times the JV_max and 5.15 times the k value of the traditional Pt black-PFC system.These results were attributed to the high H₂O₂concentration generated at activated GF cathode,which increased by 24.13 times（0.402 mmol/L）than Pt black cathode.In addition,the O₂·^-and HO·were 2.87(23.98×10^-5 mol/L)and 2.48 times(13.00×10^-4mol/L)as high as those in the Pt black-PFC system,respectively.This study demonstrated the feasibility of synergistically improving the performance of the self-driven PFC system by enhancing H₂O₂production at the cathode.4.The enhancement of WS₂ cocatalyst on the performance of the self-driven PFC system.The previous studies have introduced simple radical-chain reaction catalyzed by Fe³⁺/Fe²⁺cycle,which could obviously improve the performance of the PFC.However,the performance of PFC system was limited by the low efficiency of Fe³⁺/Fe²⁺cycle,especially in which Fe³⁺was difficult to be converted into Fe²⁺.Based on this problem,an enhanced self-driven PFC system was developed by introducing a cocatalyst of tungsten disulfide（WS₂）for efficiently degrade organics and generate electricity.In the PFC system,the exposed W⁴⁺had the ability to reduce Fe³⁺,which could greatly facilitate the conversion of Fe³⁺to Fe²⁺and significantly improve the Fe²⁺concentration.Therefore,the yield of HO·and O₂·^-were significantly improved.The results showed that the HO·and O₂·^-were enhanced by 151%(6.89×10^-5 mol/L)and 45%(3.31×10^-5 mol/L)in the Fe SO₄/WS₂/Pt system with WS₂ addition.When H₂O₂ was provided with an activated GF cathode,the HO·and O₂·^-were further improved by 204%(8.32×10^-5 mol/L)and 242%(7.79×10^-5 mol/L),respectively;meanwhile,the rate constant k went up 122%in the Fe SO₄/WS₂/GF system.Additionally,the introduction of WS₂ cocatalyst also widened the working pH range of the system,and the PFC system exhibited a stable degradation efficiency for a wide pH range from 2 to 9.This study revealed that the addition of cocatalyst WS₂ could significantly improve organics degradation and simultaneous electricity generation of the PFC system.更多还原