Near-Infrared Plasmon-Driven Nitrogen Photofixation Achieved by Assembling Size-Controllable Gold Nanoparticles on TiO2 Nanocavity Arrays

Au NPs and TiO2 with surfaceoxygen vacanciesare integrated simultaneously via a novel solid-state-dewetting technique.The plasmonic frequencies of the ordered Au NP arrays range from visibleto NIR region by controlling Au NP sizes. The NIR plasmonic N-2 photofixation is driven in a tandem process: hot electronsare activated, injected into TiO2, trapped at defect states,and reduced adsorbed N-2 molecules. Solar-driven reduction of nitrogen (N-2) toammonia (NH3) offers an alternative carbon-free strategytoward cleanerand more sustainable NH3 production compared with the traditionalHaber-Bosch process. However, the photofixation of N-2 by low photonic-energy near-infrared (NIR) light still representsa huge challenge. Here, we design an Au/TiO2 hybrid plasmonicsystem via a solid-state dewetting process to arrange Au nanoparticlesuniformly on ordered ultrathin TiO2 nanocavity arrays basedon the anodic TiO2 templates, in which the tailored goldnanoparticle arrays serve as the mediator to guarantee NIR light harvestingand energy transfer. The oxidized layer of Ti is rich in oxygen vacanciesproduced simultaneously in solid-state-dewetting process which facilitatesthe adsorption and activation of N-2 molecules. The chargetransfer and N-2 reduction reaction are driven in a tandempathway, leading to an ammonia evaluation rate of 10.1 nmol cm(-2) h(-1) under NIR irradiation, whilethe photocatalytic performance shows no obvious decay after a cycletest. Briefly, the NIR-responsive Au/TiO2 plasmonic photocatalystsystem opens a new insight to achieve a better utilization of solarenergy for photocatalytic nitrogen fixation.