Powering photoreactions with inductively coupled wireless light emitters located inside the reaction medium

• Applicant: Dr. Jonathan Bloh
• Subject Area: Technical Chemistry ; Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 419142041

Photocatalysis is the activation or acceleration of a chemical reaction by the presence of light (photons). The importance of photocatalysis in fundamental and applied sciences expanded rapidly over the last decades, especially as they are often reported as resource-efficient and sustainable. Photons are essentially traceless and, in the case of sunlight, carbon neutral reagents.However, industrial implementation of these reactions is technically challenging. Engineering limitations such as illumination efficiency and the need for special reactor designs are the main reasons for those processes still being limited to a few selected cases. Especially in the case of high catalyst loadings the penetration depth of light into the reactor, which typically does not exceed a few millimeters, is a limiting factor. Reactors for those processes need a large surface compared to their volume. Very thin reactors show better illumination efficiencies but are very area intensive in scale-up. Therefore, the requirement of specific expensive photoreactors is often a substantial obstacle for implementation in industrial scales. Internal illumination can be a solution. It is a promising technique that achieves good illumination efficiency and enables a more flexible choice of reactor types.Compared to classical methods for internal illumination, we propose resonant inductive coupling (RIC) for the powering of internal light sources, further called Wireless Light Emitters (WLEs). Since the light sources themselves can easily be added to or separated from the reactor, it allows for more flexibility in selecting a suitable reactor. Even standard multi-purpose reactors could be used. In this project, we propose utilizing WLEs to power photocatalytic reactions, which could tremendously help to wide-spread applications. Resonant inductive coupling (RIC) shows great potential for wireless powering of LED devices as the possible energy transfer efficiency is already >75% and the conductivity of water shows no negative impact on the energy transfer efficiency. Since there are already many well-known applications for RIC such as charging of smart phones and tooth brushes, synergetic effects in future developments can be expected. LEDs powered by RIC were already successfully introduced as a means to illuminate photobioreactors. The employed magnetic field is in the order of 1mT (magnetic flux density) at a frequency of about 178 kHz and is comparable to induction cooktops. While a magnetic field effect (MFE) has been proposed to affect diffusion and charge separation in the semiconductor particles, this was only observed for magnetic fields orders of magnitude higher and with controversial results. Also, the reports of positive effects on the reactivity far outweigh the negative ones so this is very unlikely to present a problem in the envisioned application.

• DFG Programme: Research Grants