A critical new research direction in solid oxide cells (SOCs) is related to balancing power-grid load or integrating heat-electricity-gas interconnection simply by switching operations between the fuel-cell and electrolyser mode. The rational design of robust and high-performance materials for SOCs is urgent for high conversion/energy efficiencies. Iron is highly abundant and offers suitable and flexible redox chemistry for the two operation modes. Iron-based oxide materials are widely investigated for SOCs because of their low cost and, more importantly, the appropriate valence stability of the Fe–O bond for excellent redox activity across a wide range of electrode functions. This review describes the progress in iron-based materials for SOCs, especially the recent applications in electrode materials or catalysts. The stable structure of the ferrite oxides provides an important platform for improved performance via the substitution of Fe in the fuel electrodes of an SOC with H₂/H₂O or carbonaceous fuel/feedstock. Furthermore, we discuss nano-sized Fe⁰ metal or alloys on an oxide electrode via infiltration and in situ exsolution aiming to fabricate highly active electrocatalysts. The advances of ferrite oxide-based oxygen electrodes are also discussed in terms of thermal expansion, stability and electrocatalysis before the developments of symmetrical and reversible SOCs based on ferrite oxides are classified and summarized. Therefore, the challenges and future prospects are discussed.

We present a study of the energy levels present in a perovskite solar cell using Kelvin probe and UV air photoemission measurements. By constructing a detailed map of the energy levels in the system we are able to predict the maximum open circuit voltage of the solar cell.

Photocatalytic conversion of cellulose to sugars and carbon dioxide with simultaneous production of hydrogen assisted by cellulose decomposition under UV or solar light irradiation was achieved upon immobilization of cellulose onto a TiO₂ photocatalyst. This approach enables production of hydrogen from water without using valuable sacrificial agents, and provides the possibility for recovering sugars as liquid fuels.

A metal-organic hybrid perovskite (CH₃NH₃PbI₃) with three-dimensional framework of metal-halide octahedra has been reported as a low-cost, solution-processable absorber for a thin-film solar cell with a power-conversion efficiency over 20%. Low-dimensional layered perovskites with metal halide slabs separated by the insulating organic layers are reported to show higher stability, but the efficiencies of the solar cells are limited by the confinement of excitons. In order to explore the confinement and transport of excitons in zero-dimensional metal–organic hybrid materials, a highly orientated film of (CH₃NH₃)₃Bi₂I₉ with nanometre-sized core clusters of Bi₂I₉³⁻ surrounded by insulating CH₃NH₃⁺ was prepared via solution processing. The (CH₃NH₃)₃Bi₂I₉ film shows highly anisotropic photoluminescence emission and excitation due to the large proportion of localised excitons coupled with delocalised excitons from intercluster energy transfer. The abrupt increase in photoluminescence quantum yield at excitation energy above twice band gap could indicate a quantum cutting due to the low dimensionality.