A widely distributed soil mineral, α-iron-(III) oxyhydroxide, was found to be a recyclable catalyst for the photoreduction of carbon dioxide to formic acid.Credit: Prof. Kazuhiko Maeda
Photoreduction of CO2 to transportable fuels such as formic acid (HCOOH) is a good way to combat rising CO2 levels in the atmosphere.To help with this task, a research team at Tokyo Institute of Technology selected a readily available iron-based mineral and loaded it onto an alumina support to develop a catalyst that can efficiently convert CO2 into HCOOH, about 90% selectivity!
Electric vehicles are an attractive option for many people, and a key reason is that they have no carbon emissions.A big downside for many, however, is their lack of range and long charging times.This is where liquid fuels like gasoline have a big advantage.Their high energy density means long ranges and quick refueling.
Switching from gasoline or diesel to a different liquid fuel can eliminate carbon emissions while retaining the advantages of liquid fuels.In a fuel cell, for example, formic acid can power an engine while releasing water and carbon dioxide.However, if formic acid is produced by reducing atmospheric CO2 to HCOOH, then the only net output is water.
Rising carbon dioxide levels in our atmosphere and their contribution to global warming are now common news.As researchers experimented with different approaches to the problem, an effective solution emerged—turning excess carbon dioxide in the atmosphere into energy-rich chemicals.
The production of fuels such as formic acid (HCOOH) by the photoreduction of CO2 in sunlight has attracted a lot of attention recently because the process has a double benefit: it reduces excess CO2 emissions and also helps minimize the energy we currently face. shortage.As an excellent carrier for hydrogen with high energy density, HCOOH can provide energy through combustion while releasing only water as a by-product.
To make this lucrative solution a reality, scientists have developed photocatalytic systems that reduce carbon dioxide with the help of sunlight.This system consists of a light-absorbing substrate (ie, a photosensitizer) and a catalyst that enables the multiple electron transfer required for the reduction of CO2 to HCOOH.And thus began to search for suitable and efficient catalysts!
Photocatalytic reduction of carbon dioxide using commonly used compound infographics.Credit: Professor Kazuhiko Maeda
Due to their efficiency and potential recyclability, solid catalysts are considered the best candidates for this task, and over the years, the catalytic capabilities of many cobalt, manganese, nickel and iron-based metal-organic frameworks (MOFs) have been explored, among which The latter has some advantages over other metals.However, most iron-based catalysts reported so far only produce carbon monoxide as the main product, not HCOOH.
However, this problem was quickly solved by a team of researchers at Tokyo Institute of Technology (Tokyo Tech) led by Professor Kazuhiko Maeda.In a recent study published in the chemical journal Angewandte Chemie, the team demonstrated an alumina (Al2O3)-supported iron-based catalyst using α-iron(III) oxyhydroxide (α-FeO​​​ OH; geothite).The novel α-FeO​​​OH/Al2O3 catalyst exhibits excellent CO2 to HCOOH conversion performance and excellent recyclability.When asked about their choice of catalyst, Professor Maeda said: “We want to explore more abundant elements as catalysts in CO2 photoreduction systems. We need a solid catalyst that is active, recyclable, non-toxic and inexpensive. That’s why we chose widely distributed soil minerals like goethite for our experiments.”
The team employed a simple impregnation method to synthesize their catalyst.They then used iron-supported Al2O3 materials to photocatalytically reduce CO2 at room temperature in the presence of a ruthenium-based (Ru) photosensitizer, electron donor, and visible light with wavelengths over 400 nanometers.
The results are very encouraging.The selectivity of their system for the main product HCOOH was 80–90% with a quantum yield of 4.3% (indicating the efficiency of the system).
This study presents a first-of-its-kind iron-based solid catalyst that can generate HCOOH when paired with an efficient photosensitizer.It also discusses the importance of proper support material (Al2O3) and its effect on the photochemical reduction reaction.
Insights from this research may help develop new noble metal-free catalysts for the photoreduction of carbon dioxide to other useful chemicals.”Our research shows that the path to a green energy economy is not complicated. Even simple catalyst preparation methods can yield great results, and it is well known that earth-abundant compounds, if supported by compounds such as alumina, can be used with as a selective catalyst for CO2 reduction,” concludes Prof. Maeda.
References: “Alumina-Supported Alpha-Iron (III) Oxyhydroxide as a Recyclable Solid Catalyst for CO2 Photoreduction under Visible Light” by Daehyeon An, Dr. Shunta Nishioka, Dr. Shuhei Yasuda, Dr. Tomoki Kanazawa, Dr. Yoshinobu Kamakura, Prof .. Toshiyuki Yokoi, Prof. Shunsuke Nozawa, Prof. Kazuhiko Maeda, 12 May 2022, Angewandte Chemie.DOI: 10.1002 / anie.202204948
“That’s where liquid fuels like gasoline have a big advantage. Their high energy density means long ranges and quick refueling.”
How about some numbers?How does the energy density of formic acid compare to gasoline?With only one carbon atom in the chemical formula, I doubt it would even come close to gasoline.
In addition to that, the smell is very toxic and, as an acid, it is more corrosive than gasoline.These aren’t unsolvable engineering problems, but unless formic acid offers significant advantages in increasing range and reducing battery refueling time, it’s probably not worth the effort.
If they planned to extract goethite from the soil, it would be an energy-intensive mining operation and potentially damaging to the environment.
They might mention a lot of goethite in the soil as I suspect it would require more energy to get the necessary raw materials and react them to synthesize goethite.
It is necessary to look at the entire life cycle of the process and calculate the energy cost of everything.NASA found no such thing as a free launch.Others need to keep this in mind.
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