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Solar fuels and electrofuels

Our need for renewable fuels and flexible energy storage is increasing as we seek to move away from fossil fuels. This need could be met by the production of fuels from abundant resources such as water and carbon dioxide either using renewable electricity or by directly harnessing solar energy. However, challenges remain with respect to designing low cost and efficient catalysts and light harvesters, as well as constructing systems that could work at scale. Here, we assemble expert reviews and opinions, alongside some of our favourite research published in Nature Energy over the past year, that address this complex task.

Editorial

Production of fuels from water and CO2 using renewable energy could provide energy storage solutions and reduce our dependence on fossil fuels. This month, we showcase recent efforts to advance understanding in this area.

Editorial | | Nature Energy

Comment

A wealth of candidates are being investigated to improve the catalysts found in acidic and alkaline electrolysers. However, attention should be focused on developing stable water oxidation catalysts with improved intrinsic activity — not only increased geometric activity — alongside best practice for data collection.

Comment | | Nature Energy

Reviews

Articles

While the two individual half-reactions involved in visible-light-driven water splitting are well studied, producing H2 and O2 simultaneously on a single particle remains challenging. Here, the authors achieve this by decorating CdS nanorods with both Pt nanoparticles and molecular Ru complexes to catalyse the evolution of H2 and O2, respectively.

Article | | Nature Energy

Semi-artificial photosynthetic systems combine natural and synthetic features to overcome limitations of each approach to produce solar fuels. Sokol et al. integrate a dye-sensitized TiO2 photoanode with the natural machineries, photosystem II and hydrogenase, to split water without additional applied bias.

Article | | Nature Energy

For photo-electrochemical hydrogen production to become viable on a large scale, not only efficiency but also power density must be optimized. Here, the authors explore the impact of thermal integration on photo-electrochemical devices driven by concentrated solar irradiation and design one that operates with high efficiency and power density output.

Article | | Nature Energy

Conventionally, the two half reactions involved in water electrolysis occur simultaneously, presenting materials and process challenges. Here, the authors decouple these to split water efficiently in two steps: electrochemical hydrogen evolution, followed by spontaneous oxygen evolution at elevated temperature.

Article | | Nature Energy

Electrochemical CO2 reduction to fuels and chemicals is typically accompanied by oxygen evolution as the anodic half reaction. Here, Verma et al. identify glycerol oxidation as a viable alternative half reaction, reducing cradle-to-gate CO2 emissions and improving the economics of CO2 conversion.

Article | | Nature Energy

Liquid products from electrocatalytic CO2 reduction are often mixed with additional solutes in the electrolyte, meaning that downstream separation is required. Here, the authors design cells that use solid electrolytes to generate flows of CO2-derived liquid fuels with high concentrations that are free of extraneous ions.

Article | | Nature Energy