Bottom-up synthesis of high surface area mesoporous crystalline silicon and evaluation of its hydrogen evolution performance.

As an important material for many practical and research applications, porous silicon has attracted interest for decades. Conventional preparations suffer from high mass loss because of their etching nature. A few alternative routes have been reported, including magnesiothermic reduction; however, pre-formed porous precursors are still necessary, leading to complicated syntheses. Here we demonstrate a bottom-up synthesis of mesoporous crystalline silicon materials with high surface area and tunable primary particle/pore size via a self-templating pore formation process. The chemical synthesis utilizes salt by-products as internal self-forming templates that can be easily removed without any etchants. The advantages of these materials, such as their nanosized crystalline primary particles and high surface areas, enable increased photocatalytic hydrogen evolution rate and extended working life. These also make the mesoporous silicon a potential candidate for other applications, such as optoelectronics, drug delivery systems and even lithium-ion batteries.