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Engineering Silicon Carbide Nanowires for Solar Fuels Production

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Nanowire research could herald new generation of portable solar-fuel-powered devices

EU-funded scientists have developed nanomaterials that can be scaled up to produce a new generation of solar-powered devices with the potential to replace batteries or bulky solar panels.

Energy

Solar fuels, synthetic chemical fuels produced using sunlight for photosynthesis, are a promising renewable alternative to fossil fuels which could reduce carbon emissions. EU-funded researchers under the SOLARFUELS project have developed a new process to produce aligned silicon carbide nanowires at scale, opening the way for nanowires to be used in the design of future portable solar-fuel-powered devices that have the potential to replace bulky solar panels and batteries. Nanomaterials have a high surface area, increasing energy conversion efficiency, whilst silicon carbide nanowire semiconductors show efficient photocatalytic performance in visible light. Aligning the nanowires makes it easier to control light harvesting capacity and is a crucial step towards device design. “Aligned silicon carbide nanowires that promote light harvesting and electron transfer can be harnessed to convert solar energy,” says Jindui Hong, who received a two-year Marie Skłodowska-Curie fellowship to conduct the research at Oxford University in the UK. “We have now shown this conversion. More than that, we have measured it using an in situ diagnostic tool that we also developed as part of the previous EU-funded DEDIGROWTH and DEVICE projects,’ says SOLARFUELS project coordinator Nicole Grobert, professor of nanomaterials at Oxford. “We measured the mass of the molecules being released that was previously predicted only in theory for the carbon nanotube-silicon carbide conversion,” she says. “It is the first time experiments were conducted to monitor the conversion reaction in situ to understand how these nanowires are formed.” “By changing the chemistry of carbon nanotubes and creating silicon carbide nanowires we have control over the band gap which you don’t necessarily have with conventional multi-wall carbon nanotubes,” she explains, referring to the multiple rolled carbon layers of previous research, which have different properties. Scaling up The main bottleneck for using nanomaterials in industrial applications is to be able to manufacture at scale without changing the properties of the material, with most research into photosynthesis using nanomaterials is based on experimental observation of a few molecules or milligrams invisible to the naked eye. Oxford University’s laboratory is already set up for large production of aligned carbon nanotubes, so a carbon nanotube template was used to produce the aligned silicon carbide nanowires. “We came up with a recipe that allowed us to create gram-scale silicon carbide nanowires. When we tested them it showed that they were efficient in photocatalytic reaction under visible light,” Professor Grobert says. “We now have enough nanomaterial to create a lightweight portable device, which could be used on the go.” Designing and creating a pocket-sized device will be the work of a new project. As sunlight is mainly visible light, “to be able to harvest visible light and convert it into energy is a winner. We can just shine light onto something, eliminating the need for transformers and the extra step of energy generation,” explains Professor Grobert. “In a process that needs energy you can channel the sunlight straight into the application.” Purifying water Though the initial aim of the project was to use nanomaterials for energy conversion, researchers also found that the silicon carbide nanowires reduce water contamination in visible light in a very short period of time. “It is active in degrading pollutants in water and can work both under visible light and ultra-violet light,” Dr Hong says.

Keywords

SOLARFUELS, energy, renewable energy, solar energy, solar fuel, nanowires, nanotechnology, materials, battery technology, DEDIGROWTH, DEVICE

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8 June 2020