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Artificial photosynthesis. Artificial photosynthesis - an alternative source of energy? Chlorophyll is more effective than Akinfeev, but this is not enough

Photosynthesis, the ability of plants, using the energy of sunlight, to oxidize water with the release of oxygen, is the most important evolutionary acquisition of nature. Scientists from all over the world, including from the USA, Japan and the European Union, have been struggling for more than 30 years to replicate natural technologies and create artificial photosynthesis. However, until now it has not been possible to replicate the achievements of nature as effectively. Until recently, the main problem with artificial photosynthesis was the speed of reactions. The fastest methods so far have achieved reaction rates two orders of magnitude lower than those that occur under natural conditions.

Recently it became known that researchers from the Royal Institute of Technology (KTI) in Stockholm managed to obtain a molecular catalyst that can oxidize water into oxygen as quickly as plants. The research results are extremely important and allow us to create more efficient technologies for using solar and other types of renewable energy.

A team of scientists led by Professor Licheng Sun has created a record-breaking fast molecular catalyst. While natural photosynthesis occurs at a rate of 100 to 400 transformations per second, the new catalyst reaches a speed of more than 300 transformations per second.

“This is definitely a world record and a real breakthrough in artificial photosynthesis,” explained Professor Licheng Sun.

According to the professor, this fact opens up many new opportunities for renewable energy: “Such speed will make it possible in the future to create industrial equipment for the production of hydrogen in the Sahara, where sunlight is abundant.”

Given the rapidly rising prices for petroleum fuels, the use of a new molecular catalyst will lay the foundations for many important changes. It can use sunlight to convert carbon dioxide into various fuels, such as methanol. Technologies can be developed to directly convert solar energy into hydrogen.

Licheng Sun added that he and his colleagues are working hard and intensively to make the technology cheap enough. “I am convinced that within ten years there could be a technology based on current research that is cheap enough to compete with carbon-based fuels,” he said.

Licheng Sun worked in the field of photosynthesis research for almost twenty years, more than half of his tenure at the Royal Institute of Technology. Based on his experience and the opinions of his colleagues, the professor believes that an effective catalyst for water oxidation is the key to solving solar energy problems.

In 1976, Dr. Joseph Katz, of Aragon Nat., Illinois, USA, created the "artificial leaf", as the press called the discovery of artificial photosynthesis.

It was actually a fuel cell produced during one of the stages of photosynthesis, namely the one in which photons collide with chlorophyll, releasing electrons. The discovery is a source of cheap energy from water and chlorophyll, as well as a source of hydrogen, which is considered an ideal fuel. At the same time, it represents an important step towards the artificial synthesis of organic substances (carbohydrates and fats).

Photosynthesis is a process in which, using light as an energy source, plants synthesize complex organic substances from carbon derived from simple inorganic substances (carbon dioxide). The operation takes place in specialized cellular organelles called chloroplasts, which contain the green pigment chlorophyll necessary for the action. The process is extremely complex.

In the first stage of photosynthesis, chlorophyll absorbs photons of light from solar radiation and produces an equivalent number of electrons in response. These electrons lead to the formation of enzymes necessary for the subsequent stages of photosynthesis. Chlorophyll restores electrons to water molecules through a process called water photolysis, which involves one of the previously formed enzymes catalyzed by structures containing manganese and calcium atoms. Water molecules are split into hydrogen and oxygen ions; Hydrogen is involved in chemical reactions that lead to the formation of ATP molecules, and oxygen is released into the atmosphere and used by countless organisms for respiration.

In the second stage, plants absorb from the atmosphere and, using a series of enzymes in a chain of complex operations, build carbohydrates such as sucrose or starch, and from them other organic substances, from the carbon released from CO2.

In this process, its efficiency is important: almost nothing is lost, biochemical cycles work with great speed and precision that seem implausible, enzymes are constantly recycled and revived.

Photosynthesis is a phenomenon that, despite being studied to the smallest detail, is still a miracle.

Recently, a team of researchers from the Massachusetts Institute of Technology (MIT) led by Professor Daniel G. Nocera announced that they have produced what they call the "first artificial leaf": a mini solar panel the size of a playing card, made from a low-cost, stable and wear-resistant material. a semiconductor material coated with catalyst compounds that, when immersed in water, mimics the process of photosynthesis with a high degree of efficiency.

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Photosynthesis is the conversion of plant energy into chemical energy. Under the influence of electromagnetic radiation in the visible spectrum, water and carbon dioxide are converted into molecular oxygen and glucose, and water is also divided into hydrogen and oxygen.

Thus, artificial photosynthesis has two directions and tasks:

  • Conversion of carbon dioxide from the atmosphere (combating the greenhouse effect, pollution and as a by-product - fuel and other compounds).
  • Production of hydrogen from water, which will be used to generate electricity and as fuel.

Artificial photosynthesis became possible thanks to the use of artificial nano-sized supramolecular systems.

Carbon dioxide conversion

The operating principle of the artificial photosynthesis system involves the conversion of atmospheric carbon dioxide into organic compounds using light energy.

The resulting chemical formations will be used in the future to produce fuel, various types of plastics and pharmaceuticals. Apart from solar energy, the chemical reaction does not require additional power sources.

Artificial photosynthesis technology converts carbon dioxide into methanol. The innovative system is powered by special bacteria and the energy of sunlight. This development will allow humanity to reduce the use of fossil fuels - coal, oil and natural gas.

The technology for converting CO2 on an industrial scale should change many negative processes on the planet from an environmental point of view. In particular, many experts see this direction as a way to combat global warming.

Artificial photosynthesis installation option

In the process of natural photosynthesis, leaves use the energy of the sun to process carbon dioxide, which reacts with water and forms the biomass of the plant. In a system of artificial photosynthesis, nanowires made of silicon and titanium dioxide receive solar energy and deliver electrons to the bacteria Sporomusa ovata, due to which carbon dioxide is processed and reacts with water, yielding various chemicals, including acetates.

Genetically modified Escherichia coli bacteria are capable of transforming acetates and acetic acid into complex organic polymers, which are the “building blocks” for the production of polymers RHB, isoprene and biodegradable n-butanol. The resulting compounds are found in common chemical products, from paints and varnishes to antibiotics.

Artificial leaf

Through the efforts of the English scientist Julian Melchiorri, a synthetic leaf capable of performing the functions of photosynthesis was developed. The artificial green leaf uses chloroplasts obtained from ordinary plants. According to the technology, chloroplasts are placed in a protein medium, thanks to which they are evenly distributed throughout the thickness of the liquid and do not coagulate. It is assumed that this development will be used in urban environments to produce oxygen. It is possible that the synthetic sheet will find application in the field of space research.

Such a symbiosis of semiconductor elements with living organisms could become the foundation for the further development of a programmable photosynthesis system that would produce a wide range of organic substances using only solar energy. If the future system works correctly, humanity will be able to create plastic and combustible fuel literally from thin air.

Energy from photosynthesis

Like natural solar energy converters, artificial photosystems should consist of the following components:

  • Solar radiation catcher,
  • Reaction Center,
  • A means of storing the received energy.

The most important task being solved in laboratories is increasing the efficiency of artificial photosynthesis. Therefore, a significant part of the work comes down to finding the optimal materials for creating each of the above blocks.

A system of artificial photosynthesis with high efficiency and nanosize is expected in robotics, in particular in the field of creating nanorobots, where the issue of energy supply is one of the key ones.

Compact installations for generating energy from photosynthesis will presumably replace solar panels and wind turbines in zero-consumption homes, and also have prospects for integration into smart home systems specialized in energy self-sufficiency.

While solar panels are limited by the theoretical limits of their efficiency, somewhere there is a place for artificial photosynthesis, the long-forgotten cousin of solar panels.
It is very likely that people will continue to burn liquid and solid fuels that burn, while solar panels will only be able to provide us with electricity.

In 1912, Science published an article in which Professor Giacomo Chamician wrote the following: “Coal offers solar energy to humanity in its most concentrated form, but coal is exhaustible. Is fossil solar energy really the only thing modern life and civilization can use?” And later in the article he adds:
“Glass buildings will be everywhere; photochemical processes will take place inside them, which until now have been a guarded secret of plants, but which will be mastered by human industry, it will learn how to make them produce even more abundant fruits than nature, since nature is in no hurry, and humanity is the opposite. Life and civilization will continue as long as the sun shines."
Climate change is giving new impetus to research into artificial photosynthesis. Plants do something else useful: they capture carbon dioxide. Most climate models that get us within the Paris Agreement limit of 2 degrees Celsius require large amounts of bioenergy with carbon capture and storage. This is a negative emissions technology where plants capture carbon dioxide, turn it into biofuel and then burn it. Carbon is captured and sequestered underground.
Artificial photosynthesis can be a carbon-negative source of liquid fuels like ethanol. Environmentalists often turn to the "hydrogen economy" as a solution to reducing carbon emissions. Instead of replacing our entire infrastructure - which relies on solid and liquid fuels - we simply replace the fuel. Fuels like hydrogen or ethanol can be produced using solar energy, as in artificial photosynthesis, so we will continue to use liquid fuels with less damage to the environment. Universal electrification may be more complex than simply switching from gasoline to ethanol. Artificial photosynthesis is definitely worth exploring. And great strides have been made in recent years. Heavy investment from government and philanthropic foundations is pouring into solar fuels. Several different photochemical processes are being investigated, some of which already have the potential to be more efficient than even plants.
In September 2017, Lawrence Berkeley National Laboratory described a new process that can convert CO2 into ethanol, which can then be used as a fuel, and ethylene, which is needed to make polyethylene plastic. This marked the first demonstration of the successful conversion of carbon dioxide into fuels and plastic precursors.
A recently published paper in Nature Catalysis discussed a technique in which photovoltaic panels are connected to a device that electrolyzes carbon dioxide. The anaerobic microbe then converts carbon dioxide and water using electrical energy into butanol.
They noted that their ability to convert electricity into desired products was nearly 100% efficient, and the system as a whole was able to achieve 8% efficiency in converting sunlight into fuel. This may seem like a small number, but 20% is great for solar panels that directly convert sunlight into electricity; Even the most productive plants, such as sugarcane and millet, gain no more than 6% efficiency. That is, it is comparable to biofuels currently used, such as corn bioethanol, since corn is less efficient at converting sunlight into stored energy.
Other forms of artificial photosynthesis focus on hydrogen as a possible fuel. Harvard researchers recently unveiled an impressive version of a "bionic leaf" that can convert solar energy into hydrogen. One of its main advantages is that its effectiveness increases rapidly if it is allowed to “breathe” pure carbon dioxide. If we're going to live in a future where huge amounts of carbon dioxide are extracted from the atmosphere, we'll now have a pretty good use for it. Although people have been less than keen on the idea lately (the thermodynamics of using electricity to split water into hydrogen and oxygen are not always ideal), there is still research being done on fuel cells for cars and hydrogen for heating homes, especially in Japan.
One of the problems with any effort to create artificial photosynthesis is that the more steps you have in the conversion process, the more energy will be lost along the way. Using electrified appliances with energy generated directly from the sun will be far more efficient than any scheme to turn electricity and carbon dioxide into fuel, which you then burn to regenerate the share of electrical input.
Moreover, from an environmental and practical point of view, building billions of artificial plants may be much less feasible than planting seeds for a few well-chosen biofuels. On the other hand, these plants often require good soil, which quickly deteriorates due to agricultural pressure. Biofuels have already been suspected of using land that could feed a growing population. The good thing about artificial photosynthesis is that you can see these “plants” thriving in the desert or even the ocean.
As often happens, we draw inspiration from nature - but understanding it, subduing it and even improving it poses a problem for us.