SEMINAR

The sluggish and complex multi-step oxygen evolution reaction (OER) remains an obstacle to bias-free photoelectrochemical water-splitting systems. Several theoretical and experimental studies have suggested that OER efficiency can be significantly enhanced in chiral material-based photoanodes by utilizing the chirality-induced spin selectivity (CISS) phenomenon. The final product at the photoanode is the oxygen molecules, where the spin alignment of intermediate radicals is favorable to the generation of triplet ³O₂ (most stable molecular oxygen species). Considering the energy difference between a singlet ¹O₂ and triplet ³O₂, spin-dependent chemical reactions combined with the CISS phenomenon can play a crucial role in the OER process. Moreover, chiral material-based photoanodes are capable of paralleling spin distribution on the catalytic surface. The resulting spin-aligned intermediate radicals can promote the generation of spin-allowed triplet ³O₂ over that of singlet oxygen, while hindering the formation of hydrogen peroxide, in turn leading to the enhanced STH efficiency.  In this regard, chiral materials (as a spin-filter layer) have been recognized as promising candidates for achieving a breakthrough in the solar-to-hydrogen efficiency of water-splitting devices. Herein, we report that the CISS phenomena can become an impressive approach by adopting chiral 2D organic-inorganic hybrid perovskites (OIHPs) as a spin-filtering layer on the 3D OIHP photoanode. Our chiral 2D OIHP-based water-splitting device achieved enhanced oxygen evolution performance with a reduced overpotential of 0.2 V, high fill factor, and increased photocurrent of 22 mA cm^–2 at 1.2 V_RHE compared to a device without a spin-filtering layer. For unbiased water splitting, a perovskite-based photocathode decorated with a spatially decoupled hydrogen evolution reaction catalyst is fabricated. This decoupled geometry enables the physical protection of the perovskite layer from the electrolyte, thus allowing excellent stability for over 100 h. To investigate the overall water splitting performance, this perovskite photocathode is connected in parallel with spin-filtering layer adopted photoanode based on chirality-induced spin selectivity. An unbiased solar water splitting was achieved using all the OIHP photoelectrodes, resulting in a remarkable unassisted solar-to-hydrogen efficiency of ~12.5% and a continuous 10 h stable operation.