| Rapid development of industrialization and urbanization has brought about increasingly serious energy crisis and environmental pollution problems.Among them,water pollution become one of the most concerns in our society.Photocatalytic fuel cells（PFC）use solar energy as the driving force to degrade waste water while recovering chemical energy in it to generate electricity simultaneously.Because of low cost,strong oxidation ability and mild reaction conditions,PFCs have shown promising perspective in wastewater treatment and renewable energy utilization.However,current photoanodes in photocatalytic fuel cells generally suffer from as low utilization efficiency of visible light,poor transport and easy recombination of photo-generated electron-hole pairs,which limit the development and application of photocatalytic fuel cells.In order to improve the performance of the photocatalytic fuel cell,this thesis is devoted to construction of highly-efficient photoanodes based on functional polydopamine（PDA）and study their photoelectrochemical activities and electricity generation.First,to enhance the energy and mass transport,a PDA-MSs/Ti O2 photoanode was proposed by using the PDA microspheres（PDA-MSs）as the template.Not only the pore structure could be regulated to enhance energy and mass transport,but also the N doping could be realized to broaden the absorption range of light.Subsequently,from the perspective of broadening the spectral absorption range of the photoanode and enhancing the transport of photo-generated carriers,a g-C3N4/Ti O2 photoanode was proposed by using the PDA coating on the Ti O2 film to adsorb g-C3N4.This strategy resulted in the formation of heterojunction to improve the light utilization and enhance the separation of the electron and hole pairs.Finally,based on the dual functions of the pore structure regulation and adsorption of PDA microspheres,a g-C3N4/N-Ti O2 photoanode was prepared to further enhance the energy and mass transport and carrier transport.The physical and chemical properties and photoelectrochemical properties of the above photoanodes were characterized.The PFC performances with these new photoanodes and the effects of operating parameters were also studied.Main conclusions of this thesis are summarized as follows:（1）Construction and performance of the photoanode based on the template of polydopamine microspheresThe PDA microspheres were firstly prepared.The prepared PDA microspheres were then added into the conventional Ti O2 photoanode during its preparation process,which were finally removed via high-temperature calcination.By doing this,a new PDA-MSs/Ti O2could be formed.Use of polydopamine microspheres as the template could not only form vigorous pore structure in the photoanode,which could enhance the energy and mass transport,but also realized the N doping,which could broaden the absorption range of light and reduce the resistance of the photo-carrier transport.Because of these merits,the photoelectrochemical activity of the developed photoanode could be improved.It should be noted that when the mass ratio of PDA to Ti O2 and the size of PDA microspheres were too large,the collapse and cracks would be formed in the photoanodes,which could result in the decreased performance.It was found that the best PFC performance was achieved with the photoanode prepared by using 220-nm PDA microspheres as the template at the ratio of 1:5（PDA:Ti O2）,which was 34.2%higher than the conventional Ti O2 photoanode.Parametric study indicated that the increase of the light intensity and reactant concentration led to the improved in-cell performance.The in-cell performance was first increased and then decreased as the liquid flow rate increased in the testing range.（2）Construction and performance of the g-C3N4/TiO2 photoanode based on polydopamine coatingA new g-C3N4/TiO2 photoanode was constructed by coating a thin polydopamine film to realize efficient adsorption of g-C3N4 nanosheets.This strategy resulted in the formation of a heterjunction between g-C3N4 and Ti O2,which could enhance the separation of the electron and hole pairs and reduce the transport resistance of photo-carriers.Meanwhile,the light absorption rage could be broadened to improve the light utilization.As a result,the performance of the newly-developed photoanode could be boosted.Experimental results indicated that when the modification time of PDA coating was 1 h and the adsorption time of g-C3N4 nanosheets was 1 h,the g-C3N4/Ti O2photoanode showed the best photoelectrochemical activity,presenting 70.4%increment as compared to conventional Ti O2 photoanode.Parametric study indicated that the increase of the light intensity and reactant concentration led to the improved in-cell performance.The in-cell performance was first increased and then decreased as the liquid flow rate increased in the testing range.（3）Construction and performance of g-C3N4/N-TiO2 photoanode based on polydopamine microspheresHerein,the g-C3N4/N-TiO2 photoanode was successfully constructed by using the functions of the template and adsorption provided by PDA microspheres.Because the PDA microspheres were used as the template,the resultant N doping and pore structure regulation could lead to the improvements in the energy and mass transport as well as the increase of the light absorption range.Besides,because the PDA microspheres could efficiently adsorb the g-C3N4nanosheets to form herejunction,which further improved the light utilization and promoted the separation of the electron and hole pairs.therefore,the synergy of the heterjunction,N doping and pore structure regulation enhanced the photoelectrochemical activity.It was found that when the adsorption time of g-C3N4nanosheets was 2 h,the g-C3N4/N-Ti O2 photoanode exhibited the best photoelectrochemical performance,which was 149.6%and 43.1%higher than that of the conventional Ti O2 and g-C3N4/Ti O2 photoanodes,respectively.It was also shown that that the increase of the light intensity and reactant concentration led to the improved in-cell performance,while the in-cell performance was first increased and then decreased as the liquid flow rate increased in the testing range. |
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