Photocatalysts are expected to be key components of nanodevices for harvesting sunlight and converting it into usable energy. However, most photocatalysts work only in the UV or near-UV regions of the solar spectrum with limited efficiency. Xiangfeng Duan and coworkers at the University of California, Los Angeles, have now prepared three-component integrated nanowire devices that serve as stable, efficient photocatalysts over a broad range of the solar spectrum (Nano Lett., DOI: 10.1021/nl101010m). In each device, a platinum-silicon photodiode is sandwiched between silver and platinum. The entire structure is encased in an insulating silicon oxide shell with only the silver and platinum ends exposed. This structure improves the system’s photostability and allows the researchers to optimize photoelectrochemical reactions. The devices have an average quantum efficiency of about 45% across the visible and near-infrared regions, and they are more stable than TiO2 photocatalysts. The researchers used the devices to catalyze formation of formic acid from CO2 and H2. They propose that such devices could be useful for environmental remediation, artificial photosynthesis, and solar fuel production.