SunUP - Solar photochemical H2 production through novel routes

The sun is an almost inexhaustible source of energy, which we have problems utilizing. Using solar cells to harvest energy is well known, although solar cells themselves still have great room for improvement. Less well known is the use of sunlight directly to drive chemical processes, such as producing hydrogen from water and other light-driven processes. The challenge today is that good catalysts for such photochemical processes only use UV-light and thus only absorb a very small part of the sunlight spectrum. If we can increase the proportion of sunlight that can be used for such catalysts, the energy gain will be very large. In this project, we turn the problem around and try to change the properties of the sunlight so that they are better suited to the good catalysts used today. To do this, we use a principle called upconversion to turn visible sunlight into UV, which drives the photocatalysis. The upconversion principle has been known since the 1960s and is used today in many technologies, but no one has so far managed to effectively upconvert sunlight, mainly because such systems absorb light very poorly. To increase efficiency, we need to add a component that absorbs sunlight effectively and is able to pass it on to the upconversion system without losing power along the way, a so-called sensitizer. It has proven difficult to find a sensitizer that is well suited and even less that can be combined with the upconversion material. This is where the solution in the SunUP project lies. By effectively combining sensitizers with upconversion materials, we open up radically new possibilities for changing light using upconversion. Our sensitizers consist of larger molecules with high absorbency. These must absorb the sunlight well and in addition have some properties that mean that they can be easily placed in the structure where we want it. A general disadvantage of such sensitizers is that they are large molecules that require high temperatures to be supplied through the gas phase. Through SunUp, we have developed a new efficient chemistry that opens up the use of other types of reactive groups that require less to be brought into the gas phase. This has opened the way for efficient deposition at lower temperatures, but also for using a new class of large molecules.

Prosjektet har utviklet ny kjemi og teknologi for deponering av store organiske molekyler via gassfase. Denne kjemien har stort potensiale både for effektiv deponering ved lave temperaturer, men også for bruk av større molekyler ved høyere temperaturer ved at mer termisk stabil kjemi kan brukes.

The aim of this project is to radically improve solar hydrogen production, by developing materials that effectively turn visible light into UV light. High energy photons can drive chemical reactions, destroy DNA and split water into its elements. Utilizing this force allows us to produce green hydrogen from light and water alone, through photocatalysts like TiO2. Green hydrogen is a core concept in EU’s Green Deal where it acts as cornerstone in decarbonizing the energy system. This usually means using renewable energy to run electrolysis of water. Solar photochemical hydrogen on the other hand eliminates the electrolysis step altogether. However, the amount of UV in sunlight is too small to effectively drive the photocatalysts directly. Decades of research have focused on increasing the photocatalysts absorption of sunlight, unfortunately often at the expense of chemical conversion efficiency. If we instead could effectively convert sunlight to UV, we can use already well-established photocatalysts like TiO2 that have a high chemical efficiency but limited utilization of sunlight. By efficient and broadband upconversion of visible sunlight to UV, SunUP will radically enhance the efficiency of solar-to-hydrogen production by combining the high hydrogen production efficiency of photocatalysts such as TiO2 with a novel sensitized upconversion nanocomposite materials.