A new porous silicon photocatalyst that generates hydrogen from water with help from sunlight could find applications in optical electronics, biosensors and batteries. Micrograph of porous silicon showing holes where salts were removed. Images courtesy of Pennsylvania State University. A mesoporous crystalline silicon, the material touts large surface area and tunable pore size through a “self-templating pore formation process,” according to researchers from Pennsylvania State University. “This porous silicon can generate a good amount of hydrogen just from sunlight,” said Donghai Wang, an assistant professor of engineering at Penn State and one of the researchers. Wang said porous silicon is typically produced by etching, a process that wastes a lot of material. In their study, Wang and colleagues discovered a chemically based method to build the porous material using silicon tetrachloride, an inexpensive source of silicon. Schematic of porous silicon. The material is then treated with sodium potassium alloy, which serves as a reducing agent. Once the process is complete, the material has numerous pores that range in size from 5 to 15 nm. Wang said the process could lead to a new type of porositic silicon and ultimately could be “scaled up to manufacturing size.” The work was funded by the U.S. Department of Energy and the Defense Threat Reduction Agency. The research is published in Nature Communications. For more information, visit www.psu.edu.