Spin-Polarized Oxygen Evolution in Chiral-Molecule-Modified Plasmonic Photoanodes
Photoelectrochemical oxygen evolution is limited not only by multi-electron charge-transfer kinetics but also by the spin constraints associated with forming triplet O2. Here, we used a hybrid photoanode architecture to demonstrate spin-polarization of plasmonic hot holes through a chiral molecular layer. TiO2 photoanodes were modified with achiral Au nanoparticles to introduce visible-light plasmonic absorption, functionalized with cysteine as a chiral molecular interface, and coated with a NiFe-based oxygen-evolution catalyst. Wavelength-resolved photo-scanning electrochemical microscopy was used to directly detect locally evolved O2 under operando illumination while simultaneously monitoring the photoanode current. Chiral functionalization with homochiral L-cysteine enhanced both photocurrent and local O2 evolution relative to racemic DL-cysteine controls. The chirality-dependent enhancement was most pronounced under visible excitation overlapping the Au plasmon resonance, including a 130% photocurrent increase. These results provide evidence that chiral molecular layers, often used for chiral nanoparticle synthesis, can directly modulate plasmon-derived hot-carrier transfer through the chiral induced spin selectivity (CISS) effect. This work establishes a chiral plasmonic photoelectrochemical platform for coupling hot-carrier generation to spin-dependent water oxidation.