Bipolar Visible Light Responsive Photocatalytic Wastewater Fuel Cell

The wastewater resource is the key and difficult issue in the filed of wastewatertreatment. The development of sustainable technology with saving resources andenergy for the wastewater treatment and recycling is a promising way for thewastewater resource. Microbial fuel cell (MFC) has attracted many attentions byproducing electricity at the same time the organic matter is biodegraded. However, itis limited due to its complicated electron transfer process, low efficiency and bacteriacultivation, etc. Based on the mismatched Fermi level between photoelectrodes, avisible light responsive PFC system comprising of photoanode and photocathode ispresented. A novel hydrothermal process for preparing WO3/W photoanode is firstlydeveloped. Then, the photocathodes material including Cu2O/Cu and Pt/PVC ispresented to couple with WO3/W to fabricate the PFC system. As-established PFCsystem can be used for wastewater treatment and electricity generation, as well ashydrogen production.The preparing of WO3/W photoanode with highly-ordered nanostructure. Beforereaction, the tungsten sheet was pre-annealed to produce a thin-layer WO3on surfaceto serve as seeded sites for crystal growth in hydrothermal reaction, which alsoprovided a strong connection between the growing WO3and substrate. Polyethyleneglycol (PEG) was used as the structure-directing agent to confne the crystal growth.The PEG molecules can be easily adsorbed at the surface of oxide colloids andconfines the growth in a certain direction. The nanostructural WO3crystal can beformed by the hydrothermal reaction. This preparation route provide a natural androbust combination between the WO3and the substrate, which obviously facilitatedthe charge transfer and reduced the recombination of photoexcited electron/hole. TheWO3/W photoanode can absorb the light at the wavelength of480nm with thebandgap of2.6eV, and exhibits the photocurrent of2.35mA/cm2, which is suitablefor water splitting and organic compound degradation. The development and application of bipolar visible light responsive PWFCsystem—WO3/W-Cu2O/Cu. The PWFC system comprises of the WO3/W photoanodeand Cu2O/Cu photocathode, and based on that the Fermi level of WO3/W photoanodeis higher than that of Cu2O/Cu photocathode. An interior bias can be produced basedon which the electrons of WO3/W photoanode can transfer from the external circuit tocombine with the holes of Cu2O/Cu photocathode then generates the electricity. Inthis manner, the electron/hole pairs separations at two photoelectrodes are facilitatedto release the holes of WO3/W photoanode and electrons of Cu2O/Cu photocathode.Organic compounds can be decomposed by the holes of WO3/W photoanode due toits high oxidation power. The short-circuit of this system can reach205μA/cm2. Theresults demonstrated that various model compounds including phenol, Rhodamine B,and Congo red can be successfully decomposed in this PWFC system, with generatingthe stable electricity.The bipolar visible light responsive PEC for spontaneous hydrogen production. APt-catalyst-decorated crystalline silicon photovoltaic cell (Pt/PVC) was prepared andemployed as an effective photocathode in order to avoid the drawbacks of Cu2O/Cuphotocathode. The Pt/PVC photocathode shows excellent stability for long timeapplication. The bipolar visible light responsive PEC is established based on themismatched Fermi levels between Pt/PVC photocathode and WO3/W photoanode.,which shows a sustainable hydrogen production with the rate of0.204μmol/hcm2.The development and application of bipolar visible light responsive PWFCsystem—WO3/W-Pt/PVC. This system is established based on the bipolar visiblelight responsive PEC. By using the aeration, the electrode reaction at Pt/PVCphotocathode was changed from proton reduction to O2reduction with H2Oproduction. The performance can be enhanced because the consumption of theelectrons at Pt/PVC photocathode can be accelerated due to the combination betweenO2and H+. Both the electricity production and organic compounds degradation ratecan be increased. The result showed that the short-circuit can reach350μA/cm2which improve70%compared with the WO3/W-Cu2O/Cu system. Methylene blue was used as the model recalcitrant organic compound in the PFC system, which couldbe completely removed after90min with generating a stable photocurrent.