Tungsten sulfide co-catalytic radical chain-reaction for efficient organics degradation and electricity generation

As a new type of photocatalytic fuel cell (PFC), radical chain-reaction PFC based on the catalysis of Fe3+/Fe2+ cycle is able to significantly improve organics degradation and electricity generation, owing to the expanded radical reaction from electrodes surface to the whole solution. However, the yield of reactive oxygen radical is obviously restricted by the low efficiency of Fe3+/Fe2++ cycle, in which Fe3+ is difficult to convert into Fe2+. Herein, we developed a tungsten sulfide co-catalytic radical chain-reaction for PFC to efficiently degrade organics and generate electricity. In the tungsten sulfide molecule, the exposed W4+ has the capability of Fe3+ reduction and thus significantly improves Fe2+ concentration and the yield of hydroxyl radical (HO2 center dot) and superoxide radical (O-2(center dot-)), which are responsible for efficient organic degradation. The results showed that HO center dot and O-2(center dot-) were enhanced by 151 % (6.89 x 10(-5) mol/L) and 45 % (3.31 x 10(-5) mol/L), respectively, in a PFC system using WO3/PVC as the composite photoanode and Pt as the cathode (FeSO4/WS2/Pt system); while HO center dot and O-2(center dot-) were further improved by 204 % (7.79 x 10(-5) mol/L) and 242 % (8.32 x 10(-5) mol/L), respectively, using an activated graphite felt (GF) as cathode (FeSO4/WS2/GF system), in which in-situ H2O2 generation was enhanced. Importantly, the rate constants for RhB degradation were also highly increased by 63.1 % and 222 % in the FeSO4/WS2/Pt system and FeSO4/WS2/GF system, respectively. In particular, the PFC system exhibited a stable degradation efficiency for a wide pH range from 2 to 9 rather than just acidic conditions in traditional radical chain-reaction PFC system. Our study revealed that tungsten sulfide could effectively improve the conversion from Fe3+ to Fe2+ and thus enhance PFC performance via the radical chain-reaction.