Core–shell silicon@mesoporous TiO₂ heterostructure: towards solar-powered photoelectrochemical conversion

Core–shell heterostructured nanomaterials with mesopores have enormous potential applications in diverse fields. Herein, we report a facile extended Stöber method to synthesize core–shell heterostructured semiconducting nanomaterials with mesoporosity. Silver (Ag) metal-assisted chemically wet etched p-type silicon nanowires (Si NWs) were used as the core, and layer-controllable mesoporous n-type anatase TiO₂ was grown as the shell to successfully fabricate the core–shell p-Si@mesoporous n-TiO₂ hybrid materials. Detailed characterization reveals that the TiO₂ shell was composed of aggregated crystalline TiO₂ nanoparticles with diameters of ≈15 nm, where the TiO₂ coating thickness was tuned ≈50 nm. The interstitial pores of these nanoparticles were observed with average pore sizes of 4–8 nm. The core–shell structured p-Si@mesoporous n-TiO₂ hybrid materials were demonstrated as photocathodes for the solar-driven photoelectrochemical (PEC) production of H₂ at the semiconductor/electrolyte interface.