Science

Life sustaining processes can support a sustainable energy matrix – summaries

Nature is the inspiration for technological developments in all areas and very often for new materials. In synthesis, we have already seen how the sweat of humans and other animals inspired the use of hydrogel to cool flexible robots, and we are familiar with the search for a material as tough as the hedgehog the Brazil nut.

In these examples, attempting to achieve the same results is completely different from natural processes, although attempts are made to reproduce solutions present in living organisms.

In our universe everything tends to equalize or, as the so-called second law of thermodynamics states, the maximum level of entropy (often referred to as the degree of disruption or disorganization of a system) and consequently the minimum energy. For a living being, however, equilibrium means death. Since nobody wants to achieve this balance, that is, at the moment when the energy reaches its minimum level, we feed ourselves and the animals, for example, and thus receive matter with a high energy content.

In the traditional synthesis of materials or other substances, the process is almost always carried out step by step in order to achieve equilibrium. We combine A and B to produce C in a reaction that lasts until the three chemical species (A, B and C) are in equilibrium. Then we take C, which is already more complex, and mix it with D to get E back in equilibrium. And so on, until we have the hydrogel to cool the robot or a building material that is as tough as the Brazil nut.

However, under unbalanced conditions, the synthesis can occur simultaneously in all reactions. For example, the interaction between A and B can result in twice as much as B, known as autocatalysis, which describes an increase in the concentration of B by its own formation. If there is also an inhibition level – for example the reaction of B with C – the growth of B can be stopped with different time scales and thus fluctuations in the B concentration with moments of greater or lesser production. These vibrations lead, among other things, to patterns and structures in matter – such as spirals, pores, dendrites and multilayered organizations – that are much more complex than those obtained in conventional synthesis.

This type of self-organized structuring is ubiquitous in nature, which indicates that fluctuations in natural processes are very common. Since the structure and properties of different materials are closely related, researchers have tried to better understand these mechanisms in order to use them to obtain new materials with complex composition and structure and thus physical and chemical properties that meet the technological requirements. urgent.

In Brazil, the Laboratory for Electrochemical Dynamics and Energy Conversion of the State University of Campinas (Unicamp) has been studying self-organized electrochemical synthesis for about four years in order to obtain materials for transformations in our energy matrix in more sustainable configurations in the future. Materials for use in devices such as fuel cells, batteries and sensors.

“Classical thermodynamics has been studied a lot, things work, we can predict them, but only under equilibrium conditions. And the balance is a little boring, ”summarizes Raphael Nagao, professor at the Unicamp Chemistry Institute. “It is natural that we do the easiest part first. However, a universe of possibilities that exists between the beginning of the reaction and equilibrium is left out, and we are interested in these possibilities, ”he adds, commenting on the research the group is doing with electrochemical devices.

Well-known electrochemical devices are batteries, in which the greatest interest lies in the electric current, which is generated by the transport of charges (electrons) between the positive and negative poles (electrodes) through a solution (electrolyte). In addition to the current, however, the reduction reactions (electron gain) and oxidation reactions (loss reactions) that take place in these devices lead to the deposition or dissolution of materials on the electrodes. Electrochemical deposition, for example, is behind the nickel-plating, galvanizing and chrome-plating processes common in the automotive industry.

Typically, obtaining materials by electrochemical deposition or dissolution is done in a more conventional approach where oscillations in major variables such as current and potential are undesirable and therefore avoided.

The goal of researchers who have worked with self-organization is to better understand what is getting out of whack and how to precisely control and streamline the growth of patterns and structures. Nagao cites the example of copper-based materials, which are essential for reducing CO2 (chemical reaction, not reducing the amount, although one leads to another). This reduction reaction aims to convert the greenhouse gas into fuels and chemicals with high added value.

“We are aware of some electrochemical systems that can be used to manipulate the structure of copper and copper oxide. Our idea is to synthesize these materials in a self-organized manner, control the structuring and then check whether there is a difference in terms of the efficiency of CO2 conversion compared to the separation under conditions under which no vibrations occur. “, He explains.

However, the area is still new and requires a lot of basic research as well as studies of possible technological effects. “Although there is a mathematical foundation for studying systems that are out of equilibrium, we are still far from having a deep understanding of what is happening. However, we cannot fail to examine whether it is possible to use these mechanisms that we find in living things and that are so successful in our syntheses, ”concludes Nagao.

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