Performance characteristics of a membraneless solar responsive photocatalytic fuel cell with an air-breathing cathode under different fuels and electrolytes and air conditions

In this work, a membraneless photocatalytic fuel cell (PFC) with a solar responsive photoanode and an air-breathing cathode was developed to simultaneously degrade the wastewater and generate electricity. The performance characteristics of the developed PFC was examined for the real application purpose. Particular attention was paid to investigate the effect of the fuel and electrolyte types on the cell performance. Experimental results showed that the alkaline electrolyte yielded the maximum power density of 4.1 mW cm−2, which was much better than the neutral electrolyte with the maximum power density of 0.5 mW cm−2. Long-term performance measurements also showed that the cell performance was rather stable under the alkaline electrolyte but dramatically reduced under the neutral electrolyte in the 3-hour constant current density operation. Regarding the fuel types, the PFC exhibited appreciable performance for both alcohols and saccharides. Methanol and glycerol produced the maximum power densities of 4.08 and 2.58 mW cm−2, while D-glucose and D-xylose generated the maximum power densities of 3.92 and 3.67 mW cm−2, respectively. The difference in the cell performance can be attributed to the difference in the molecular structure, i.e., the fuel with a simpler molecular structure and a shorter carbon chain could yield better performance. Besides, the PFCs also showed favorable performances in some complex wastes, such as artificial sewage, Coca Cola and urine. For the air-breathing cathode design, the oxygen concentration effect on the PFC performance was also studied. It was found that increasing the oxygen concentration from 5% to pure oxygen led to the improvement of the maximum power density from 3.5 to 5.2 mW cm−2.