Easy nanostructuring of iron with a helium bombardment
A foamy surface of iron oxides to convert solar energy directly into hydrogen, that is the goal of PhD candidate Irem Tanyeli at the Dutch Institute for Fundamental Energy Research (DIFFER). The physicist is working on producing hydrogen from sunlight (photocatalysis), using only abundant materials. In the scientific journal Advanced Materials and Interfaces, Tanyeli describes how to turn ordinary iron into a highly porous nanostructured surface using a simple helium-ion assisted technique.
In order to convert solar energy to hydrogen, a material is needed that can efficiently capture licht and transport it to a reaction site where water is split into hydrogen and oxygen. Metal oxides with a foamy surface structure at the nanoscale are good candidates for such photocatalysis due to their large surface area. In earlier research, Irem Tanyeli and colleagues have showed that she could turn a tungsten metal surface into nanofoam with a stream of relatively cold, dense helium plasma. As the helium is absorbed and accumulates below the surface, helium bubbles are formed and break open into a foamy structure. After oxidation, this structure works as a photocatalyst to split water and create hydrogen.
Foam to order
Tanyeli's new results in Advanced Materials and Interfaces show that her foaming technique not only works with tungsten, but also with the widely available metal iron. The experiments further demonstrate that the researcher has developed precise control over the nanofoam's characteristics. By setting the surface temperature and the duration of the plasma bombardment, she can tune the size and shape of the resulting nanostructures. In follow-up research, Tanyeli wants to investigate the efficiency of the new photocatalyst. The tungsten nanofoam from her earlier experiments has shown performance similar to existing photocatalysts, with the material producing a photocurrent around 1 mA/cm2 at 1,23V.
Solar fuels: storing sustainable energy as a fuel
An energy infrastructure with a large share of sustainable, fluctuating sources such as sun and wind requires an efficient way to store and transport energy to when and where it is needed. In its solar fuels program, DIFFER is working on converting sustainable electricity into the energy of chemical bonds. The institute focuses on efficient recycling of CO2 into methane and on hydrogen production. Such fuels offer a much higher energy density than electrical storage and are a better match to the existing energy infrastructure.