Hematite-based solar water splitting: challenges and opportunities

Abstract

As the most commonly encountered form of iron oxide in nature, hematite is a semiconducting crystal with an almost ideal bandgap for solar water splitting. Compelled by this unique property and other advantages, including its abundance in the Earth's crust and its stability under harsh chemical conditions, researchers have studied hematite for several decades. In this perspective, we provide a concise overview of the challenges that have prevented us from actualizing the full potentials of this promising material. Particular attention is paid to the importance of efficient charge transport, the successful realization of which is expected to result in reduced charge recombination and increased quantum efficiencies. We also present a general strategy of forming heteronanostructures to help meet the charge transport challenge. The strategy is introduced within the context of two material platforms, webbed nanonets and vertically aligned transparent conductive nanotubes. Time-resolved photoconductivity measurements verify the hypothesis that the addition of conductive components indeed increases charge lifetimes. Because the heteronanostructure approach is highly versatile, it has the potential to address other issues of hematite as well and promises new opportunities for the development of efficient energy conversion using this inexpensive and stable material.

Electrochemical tuning of layered lithium transition metal oxides for improvement of oxygen evolution reaction

“…We introduced an additional three transition metals (Ni, Fe and Mn) into the pristine LiCoO 2 structure to form a series of Co-based mixed metal oxides: LiCo 0. 5 Fig. 4a; Supplementary Fig.…”

“…To demonstrate the general efficacy of this electrochemical tuning methodology for OER, we further examine a series of Co-based alloy oxides including LiCo 0. 5 O 2 shows the best performance with onset potentials of B1.47 V versus reversible hydrogen electrode (RHE) and B1.525 V at 10 mA cm À 2 , even better than commercial Ir/C catalyst and comparable to the best OER catalysts reported so far 8,14,15 .…”

“…W ater splitting with the assistance of either electricity or sunlight is able to provide a sustainable source of hydrogen, which is regarded as a clean energy carrier for powering fuel cells and reducing CO 2 to fuels [1][2][3][4][5][6] . One of the critical steps is oxygen evolution reaction (OER), which can be expressed as equation (1) in base solution.…”

Aligned Fe2TiO5-containing nanotube arrays with low onset potential for visible-light water oxidation

“…Our quantum efficiency measurement for pristine Fe 2 O 3 nanotube photoanode is performed under 1.23 V versus RHE. It was reported that at a higher applied potential of 1.53 V versus RHE, the IPCE value of nanostructured Fe 2 O 3 photoanodes can increase to 45% in the 300-450 nm wavelength range 32 . Another point to note is that the performance of the composite structure is gradually decreased with increasing thickness of Fe 2 TiO 5 layer ( Supplementary Fig.…”

Facile hydrothermal synthesis of flower-like hematite microstructure with high photocatalytic properties

“…Hematite nanostructures are extensively studied for solar water splitting [1,2], new lithium battery materials [3], water treatment [4], etc. Over the past few years, various hematite nanostructures, such as nanoparticles [5], nanowires [6] and nanotubes [7] have been prepared with a variety of methods.…”