A nano-modified Si/TiO2 composite electrode for efficient solar water splitting

Solar water splitting with a composite polycrystalline-Si/doped TiO2 thin-film electrode is proposed as a promising new approach to high-efficiency and low-cost solar-to-chemical conversion. The advantage, efficiency, stability, and some problems to be solved are reviewed mainly on the basis of reported results. It is shown that (1) an n-Si electrode with surface alkylation and metal nano-dot coating gives an efficient and stable photovoltaic characteristic, (2) TiO2 (and similar metal oxides) doped with other elements, such as nitrogen and sulfur, can cause water photooxidation (oxygen photoevolution) by visible-light illumination, and thus (3) a coupling of these two electrodes is effective for efficient water splitting under solar illumination.