Band-Edge Energetics Control for Solar Hydrogen Production

The global transition from fossil-based resources to renewable energy is critically important to address the sharply increasing threat of global climate change and to ensure long-term energy security. One attractive candidate to substitute for conventional fossil fuels is hydrogen. Hydrogen is an excellent energy carrier that can be directly converted into electricity via fuel cells, or be combined with carbon dioxide (CO2) or carbon monoxide (CO) to form high energy density synthetic fuels. Most of the current industrial methods for hydrogen production, however, is by steam reforming of natural gas, which releases CO2 as a by-product, making it environmentally unsustainable. Photoelectrochemical (PEC) water splitting, on the other hand, is a carbon-neutral approach that enables the conversion and storage of the abundant solar energy into hydrogen using only renewable and clean resources. This process uses semiconductors to capture and convert sunlight into photogenerated charge carriers (i.e., electrons and holes), and electrocatalysts to facilitate the multi-charge transfer process for the oxidation and reduction of water to oxygen and hydrogen, respectively.