Bias-Free Highly Efficient and Stable Dye-Sensitized Photoelectrochemical Cells via Cascade Charge Transfer

Abstract

Dye-sensitized photoelectrochemical cells hold promise for artificial photosynthesis but face challenges such as low photocurrents and limited stability. To address these limitations, a cascade-type dye-sensitized photoelectrode is developed by encapsulating a dye-sensitized TiO2 layer and redox mediator within platinum-sputtered nickel foil. This buried-junction design enables spatially controlled cascade charge transfer, featuring effective photoconversion and Ni-catalyzed water oxidation, while suppressing undesirable recombination current leakage. Through a comprehensive study involving the selection of redox mediators and water oxidation catalysts, the best-performing photoelectrode for water splitting achieves a photocurrent of 14.0 mA cm-2 at 0.72 V vs. reversible hydrogen electrode (RHE), a Faradaic efficiency of 98%, and photostability of 30 hours. Moreover, the versatility of our design extends to bias-free H2O2 production, achieving a photocurrent density of 7.83 mA cm-2, a Faradaic efficiency of 92.2%, and a record-high solar-to-fuel efficiency of 4.15% (2.13 mu mol min-1 cm-2), with photostability of 150 hours.