自支撑阴极用于宽pH域原位产H2O2及其耦合UV降解卡马西平

A Self-Supporting Cathode for In-situ Electro-Generation of H2O2 in Wide pH Range and Its Combination with UV for Carbamazepine Degradation

  • 摘要: 阴极电催化实现宽pH域原位产H2O2颇具挑战性,但在高级氧化领域具有吸引力. 为克服传统芬顿及电芬顿技术中反应pH的限制,以Cd作为牺牲金属,以碳布为基底,通过煅烧成功合成了一种可在宽pH (3~10)条件下,均能原位电催化合成H2O2的自支撑阴极氮掺杂碳材料〔X/N@C-CC,X=550、750、950 (煅烧温度)〕,并在此基础上,通过UV活化H2O2产生氧化活性物种对卡马西平(CBZ)进行降解. 结果表明:①通过煅烧法制备的阴极材料具有高氮掺杂量,煅烧温度对其氮掺杂量及种类有着较大影响,在最佳煅烧温度750 ℃条件下,氮含量为8.89%,且以吡啶氮和石墨氮形式存在. 此外,煅烧温度对该阴极材料氧含量无明显影响,其表面均含有C=O、—COOH官能团;②催化材料的主要活性位点为吡啶氮、石墨氮以及—COOH等含氧官能团,且含氧官能团的存在,使其在碱性pH条件下亦有较好的电催化产H2O2性能;③在最佳条件下,750/N@C-CC H2O2产率可达73.09 mg/(L·h). 耦合UV后,在pH=3、6、10时均能在20 min内完全降解10 µmol/L CBZ,结合自由基掩蔽试验与电子顺磁共振(EPR)探针试验结果显示,降解CBZ的主要活性物种为·OH. 研究显示,UV耦合电催化产H2O2体系能够有效避免传统芬顿铁泥累积问题,同时反应条件不再受pH的限制,亦无有毒副产物的生成,该体系对于以CBZ为代表新型有机污染物的处理,呈现出较好的应用前景.

     

    Abstract: Electrocatalytic reduction of oxygen for in-situ electrogeneration of H2O2 remains a challenge, but it is attractive for potential applications in advanced oxidation processes. In this study, in order to overcome the limitation of working pH for traditional Fenton and electro-Fenton processes, we successfully synthesized a self-supporting nitrogen-doped carbon material (X/N@C-CC, X=550, 750, 950) via calcination at a specified temperature, using Cd as the sacrificial metal and carbon cloth as the substrate. The cathode made with this material is capable of generating H2O2 in-situ in a wide pH range (3-10), and the combination of the cathode with UV for carbamazepine (CBZ) degradation was investigated. The results show that: (1) The prepared cathode material has high content of doped nitrogen, which is greatly affected by the calcination temperature. For the investigated temperatures, 750 ℃ is the optimal one, at which Cd is almost completely volatilized, the nitrogen content is 8.89%, and only pyridine nitrogen and graphitic nitrogen are present. In addition, the increase in calcination temperature has little effect on the oxygen content of carbon materials. (2) The C=O and —COOH functional groups are detected at all temperatures, which may guarantee the superior performance of electrogeneration of H2O2 at alkaline pH condition. (3) Under the optimum conditions, the H2O2 yield of 750/N@C-CC can reach 73.09 mg/(L·h). In addition, the coupled UV-electrocatalytic H2O2 system can completely degrade 10 µmol/L CBZ within 20 minutes at pH 3, 6, or 10. The results of free radical scavenging experiments and electron paramagnetic resonance (EPR) spectra tests show that the main oxidative species responsible for CBZ destruction is ·OH. In conclusion, this system can effectively avoid the problems of sludge production, pH limitation, and formation of toxic by-products associated with the traditional Fenton process. It shows promises for treating wastewater containing emerging organic pollutants (e.g., CBZ).

     

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