Optimization of carrier transfer kinetics of BiOIO3 using TFA·/TFA- reversible redox pairs of TFA molecules as co-catalysts for efficient photoelectrochemical water splitting system

Abstract

Co-catalyst loading on photoelectrodes is considered to be an effective way to accelerate charge transfer. However, the bonding between most of the co-catalysts and photoelectrodes tends to be weak, which severely limits the role of co-catalysts in the catalytic system. Based on the above problems, we introduced trifluoroacetic acid (TFA) as a homogeneous molecular co-catalyst in the layered BiOIO3 catalytic system for the first time. The BiOIO3-TFA photoelectrode exhibited excellent photoelectrochemical performance under light and applied bias voltage. The photocurrent density reached up to 0.228 μA cm−2, which was 2.11 times higher than that before modification, while the overpotential was negatively shifted by 183 mV. The results showed that the photogenerated electron-hole pairs in BiOIO3 are excited and transferred to the TFA causing the CO double bond to break to form a TFA radical (TFA·), which is then reduced to TFA-. This cyclic redox reaction accompanied by fast hole transfer can greatly reduce the recombination behavior during carrier transport. This work demonstrates a new form of co-catalyst for photoelectrochemical water splitting. Highly water-soluble molecules and TFA·/TFA- reversible reactions have considerable potential for the development of new co-catalysts. It also provides ideas for the establishment of new, efficient catalytic systems for inhibiting carrier recombination.