Nanonet-Based Hematite Heteronanostructures for Efficient Solar Water Splitting

We report the highest external quantum efficiency measured on hematite (alpha-Fe2O3) without intentional doping in a water-splitting environment: 46% at lambda = 400 nm. This result was enabled by the introduction of TiSi2 nanonets, which are highly conductive and have suitably high surface areas. The nanonets serve a dual role as a structural support and an efficient charge collector, allowing for maximum photon-to-charge conversion. Without the addition of any oxygen-evolving catalysts, we obtained photocurrents of 1.6 and 2.7 mA/cm(2) at 1.23 and 1.53 V vs RHE, respectively. These results highlight the importance of charge transport in semiconductor-based water splitting, particularly for materials whose performance is limited by poor charge diffusion. Our design introduces material components to provide a dedicated charge-transport pathway, alleviating the reliance on the materials' intrinsic properties, and therefore has the potential to greatly broaden where and how various existing materials can be used in energy-related applications.