| With the depletion of fossil energy supplies and its combustion bringing about environmental concerns, renewable energy resources and new energy-conversion technologies has attracted more and more people attentions. Solar energy and biomass energy, the two most important sustainable energy sources, they being developed and utilized will decrease the dependence on fossil fuels, which is an ideal way for solving the energy and enviromental problems.Fuel cells have been recognized as a kind of promising and advanced energy technologies, due to their high energy conversion efficiency, low/zero emission, operation convenient and friendly, and fast response etc. The photo-assisted fuel cell（PFC） can efficient convert solar- and bio-energy into electricity simultaneously under mild conditions. In principle, the PFC catalysts are photo-responded semiconductor, the fuels are biomass molecular. The PFC with advantages of wide fuel sources, poisoning resistance, less or non-noble metal use, operated in ambient conditions and utilize renewable energy. Among, the photoelectrodes（photoanode or cathode） are the key part of PFC, to date, the researches on PFC mainly focused on photoanode, such as UV-light responded TiO2, however, the study on visible light responded photoanodes and photocathode are few.In the thesis, we studied the photoanode with visble light absorption and photocathode with photoelectrocatalytic activity to oxygen molecular, then we constructed a single photoelectrode PFC or non-platinium dual-photoelectrode PFC and investigated these photoelectrodes properties and PFCs performance. The main obtained results are as follows:（1） We synthesized bismuth vanadate（BiVO4） on FTO by electrochemical deposition. The UV-vis absorption showed that the band edge adsorption of BiVO4 was 526 nm. With Bi VO4 as photoanode, Pt/C as cathode and glucose as fuel constructed a miniature air-breathing PFC, the PFC generates electricity successful under illumination. In further, by doping W into the BiVO4, the PFC performance was increased 6.6 times of the pure BiVO4 photoanode and achieved Voc = 0.92 V, Jsc = 1.62 mA cm-2, and Pmax = 0.38 mW cm-2 under simulated sunlight(AM 1.5G, 100 mW cm-2), the efficiency（η） of solar light to electricity was estimated to be 0.38%. This remarkable enhancement is attributable to the higher charge separation and the rapid charge transfer at the electrode/electrolyte interface after W doping. In addition, we found methanol, glycerol, and cellobiose can also be the fuels to produce electricity in this PFC device.（2） We synthesized a cathode material had the good activity of photoelectrocatalysis oxygen reduction — poly（terthiophene）（pTTh）. The results showed that there was a significant improvement of ORR activity under illumination relative to in the dark, the onset potential of ORR positively shifted to 1.34 V from 0.66 V, which is 0.24 V positive than Pt/C catalyst. The result of rotating ring disc electrode（RRDE） measurements showed that the oxygen reduced in 2e- pathway on pTTh both in the dark and under illumination. Using pTTh as cathode and Pt/C as anode, we fabricated a proof-of-concept light driven H2-O2 fuel cell, the open-circuit voltage（Voc） was 0.64 V in dark and increased to 1.18 V under illuminating, the value was 0.2 V higher than the Voc of the dual Pt/C electrodes based H2-O2 fuel cell（0.97 V）. The high output was attributed to the coupling of O2 chemical reduction reaction or H2-O2 fuel cell reaction and organic solar cell.（3） Using W-doped BiVO4（W:BiVO4） as photoanode and pTTh as photocathode, We fabricated a membrane-less dual-photoelectrode PFC. The performance of W:Bi VO4–pTTh PFC under parallel and tandem illumination modes are investigated. Feeding with glucose, under parallel illumination（AM 1.5G）, we obtained the PFC performance of Voc=0.66 V, Jsc=287 μA cm-2 and Pmax=41 μW cm-2; the performance further improved by tandem illumination, the Jsc and Pmax are 2.5 and 2 times that of under parallel illumination, and achieved to 775 μA cm-2 and 82 μW cm-2, the solar conversion efficiency is ca. 0.1%. Such no membrane, non-enzymeand non-noble metal used solar-stimulated fuel cell provides an avenue for practical solar energy conversion model in a simple and low cost way.（4） Anodic electro-catalytic formic acid oxidation was studied. We synthesized a three-dimensional palladium nanoflowers（Pd-NF） composed of ultrathin Pd nanosheets by a simple solvothermal approach with oleic acid as director. The Pd-NF possessed higher activity and stability for electrocatalytic formic acid oxidation than commercial Pd/C. |
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