Tuning plasmonic p-n junction for efficient infrared-light-responsive hydrogen evolution

Infrared (IR) light, which occupies almost half of all solar energy has been an untapped energy source up to date. The solar fuel production using the IR region of light hold the key to full utilization of solar energy. The localized surface plasmon resonance (LSPR), which is tunable by the size, composition, doping ratios, is a promising phenomenon realizing the light-harvesting ability in the IR region. Here, we report the IR-responsive photo -catalyst composed of CdS and plasmonic Cu9S5, which break the record of IR-light induced photocatalytic hydrogen evolution reaction (apparent quantum yield = 4.4% at 1100 nm). Based on the simulation of the energy band at the p -n junction between plasmonic Cu9S5 and CdS, the careful tuning of the CdS domain size archived the record-breaking photocatalytic activity. The optimization of the "plasmonic " p-n junction is a key for a highly efficient IR-responsive photocatalyst.