Greenhouse Gasses Such as CO2 Could Transform Into Production of Raw Material Using Nanodiamonds

CO2 can be utilized as a raw resource for compounds necessary in manufacturing processes, including formic acid or methanol, rather than being emitted into the environment and increasing the climate change issue. In laboratory research, CO2 conversion has previously been thoroughly examined, with nanodiamonds functioning as an ecologically beneficial photocatalyst. Fraunhofer Institute for Microengineering and Microsystems IMM researchers are currently collaborating with partners to develop this response into a continuous process, putting it much closer to real-world use.

Given the harm that CO2 causes to the environment, governments and businesses are attempting to minimize their pollution to the greatest extent possible. In circumstances in which it cannot be prevented, CO2 might soon be employed as a raw resource in the creation of industrially significant C1 building blocks with only one carbon atom, like formic acid and methanol.

One proposed technique employs nanodiamonds. CO2 is transformed into formic acid in an aqueous environment by employing nanodiamonds as catalysts and incinerating them using short-wave UV-C radiation. This approach is now being researched at Prof. Anke Krüger's laboratories at the University of Würzburg (though Prof. Krüger nowadays is researching at the University of Stuttgart).

Utilizing Diamond Catalyst

The use of diamond-like catalyst may appear to be pricey; however, the diamond utilized in this procedure is not an expensive jewelry-grade diamond; rather, it is an implosion diamond manufactured on an industrial level and therefore quite affordable as a catalyst. Furthermore, because it is mostly composed of carbon, it is an ecologically benign, "green" catalyst.

Fraunhofer IMM researchers, in collaboration with Prof. Krüger as well as Sahlmann Photochemical Solutions GmbH, are now bringing these processes one step closer to real-world use as part of the CarbonCat project. To date, the investigations have been conducted in a batch reactor, also known as a stirred flask. This approach has several drawbacks, according to Dr. Thomas Rehm, a Fraunhofer IMM expert.

As a result, the research team devised a method to apply the catalyst over vast areas-specifically, reaction plates sized around 5 by 9 centimeters. The batch approach that the team has been using entails putting all of the materials in a flask and then waiting for the reaction to finish, but they want to achieve continuous operation, Rehm adds.

(Photo : Fraunhofer IMM)
A diamond-coated reaction plate with microchannels as the key element for the continuously operated flow-through reactor which converts CO2 into C1 building blocks.

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Using Visible Light

Towards that purpose, the researchers created a microreactor with just an upright reaction plate and microchannels covered with diamond catalyst. A slit at the plate's highest point is continually pumped with water. After that, the liquid pours down the plate. Capillary pressures cause a liquid layer with a depth of 10 to 50 micrometers to develop, which continually covers the microchannels. In a counterflow design, CO2 is forced over the reactivity plate from below, as described by the researchers.

This allows us to apply considerably greater levels of carbon dioxide immediately to the catalyst screen while using a much lower volume of solution. According to Rehm, this enhances the gas-liquid-solid interaction, which can result in better Conversion of co2 and hence a greater quantity of formic acid. Moreover, instead of employing energy-intensive UV-C light (as in the instance of the nanoscale catalyst), the researchers instead use visible light, which is less expensive and easier to manage.

To do this, the scientists chemically link metal complexes-organic substances with a metal core that can catch visible light-to the diamond's edge. Nevertheless, because these compounds do not cover the full surface, the liquid plus carbon dioxide continues to come into contact with the diamond surface. Whenever visible light passes on the modified covering, electrons are lifted from the diamond crystal lattice onto the diamond layer's surface. They are then transported to CO2, where they combine with water to generate formic acid.

Biocatalysis and Photochemistry Combination

As reported by TechXplore, the researchers can apply a modest electrostatic force to the diamond ground to deliver extra electrons. Certain major milestones, like the large-area catalyst as well as the utilization of visible light, have already been reached. The limited contact time is one area that the study team is still working on: the CO2, water, and diamond layer now have 10 to 15 seconds for reaction-insufficient time to create the quantity of formic acid necessary for real-world applications. The researchers are considering two options: more efficient metal combinations to boost reaction speed and modifying the reactor to allow for longer contact durations.

The limited contact time is one area that the study team is still working on: the CO2, water, and diamond layer presently only ever have 10 to 15 seconds for such reaction-insufficient time to create the quantity of formic acid necessary for real-world applications. The researchers are considering two options: more effective metal compounds to boost reaction speed and modifying the reactor to allow for longer contact durations.

The collaboration of researchers from four distinct Fraunhofer institutes is getting extra advances in the use of lighting in chemistry in a separate initiative. The idea blends photochemistry catalysis with biocatalysis (reactions in which organic enzymes function as the catalyst), bringing together two highly mild techniques. The goal is to create fine compounds with high enantiomeric purity, which is essential in industries such as medicines and agrochemicals.

The study team uses cascade-like reactions, which are made feasible by combining the two catalytic approaches. In the future, the collaboration expects to reach a high level of synergy in the synthesis of sophisticated compounds.