Nanostructured Semiconductor Photoelectrodes Complexed with Natural Photosystems I and II for Bias-Free Tandem Biophotovoltaics

Abstract

Natural photosynthesis can offer attractive models forlight-harvestingantennae, electron- and proton-transfer units, and catalytic clustersfor photovoltaics and solar fuel production. However, photoelectrodeswith natural photosystems exhibit relatively low performances dueto poor interfacial electron transfer. Here, we present efficientbias-free biophotovoltaics (BPVs) based on dual heterostructure photoelectrodescomprising natural photosystems and semiconductor nanostructures.The photocathode and photoanode were prepared using photosystem I(PSI)-protonated carbon nitride (p-C3N4) nanosheetcomplexes and a photosystem II (PSII)-TiO2 nanoparticlefilm, respectively. The linker-free complexation of PSI and PSII withnanostructured semiconductors efficiently suppressed the recombinationof photogenerated charges for efficient light harvesting and photoconversion.In particular, the oriented coupling of the negatively charged luminalside of PSI to protonated carbon nitride synergistically increasedthe photoelectron generation and charge transfer, resulting in thegeneration of a photocurrent density 28 times higher than that ofrandomly oriented PSI. Under one-sun simulated illumination, the BPVcell with the PSI-p-C3N4 and PSII-TiO2 tandem structure exhibited a photocurrent of 7.7 mu Acm(-2) without any external bias and a cell powerup to 0.9 mu W cm(-2). This work provides a simpleself-assembly method to construct efficient nanobio complex photoelectrodesbased on natural photosystems coupled with semiconductor nanostructuresin a favorable orientation for efficient and stable interfacial electrontransfer.