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Catalytic Reactions
In ancient times, enzymes were used for brewing;
In the medieval period, alchemists used saltpeter to convert sulfur to sulfuric acid;
In the thirteenth century, ethanol was transformed into ether using sulfuric acid;
In the nineteenth century, the Industrial Revolution promoted the development of science and technology, leading to the discovery of numerous catalytic phenomena. Catalytic reactions are widespread in nature and are found in various fields of chemical reactions.
It wasn't until 1835 that the term "catalysis" was introduced by the Swedish chemist Berzelius, based on his "triad theory."[1]
Catalytic reactions are categorized into various types based on the energy they consume, including thermocatalysis, photocatalysis, and electrocatalysis. Photocatalysis and photothermal catalysis, among others, are products of interdisciplinary intersections.
The emerging strategy of combining thermocatalysis and photocatalysis, known as photothermal catalysis, has gained prominence in recent years. In this article, we will explore the distinctions and connections among thermocatalysis, photocatalysis, and photothermal catalysis.
Thermocatalysis
Thermocatalysis, also known as catalysis, belongs to the realm of traditional catalysis. When it intersects with other catalytic reactions, the term "thermocatalysis" is used to distinguish its type and reaction mechanism.
Thermocatalysis mainly involves providing the energy to overcome the thermodynamic energy barrier by heating the catalytic reaction system, thereby stimulating the conversion of reactants to products with high catalytic efficiency.
Thermocatalytic reactions play a crucial role in societal development. Industries such as petroleum refining, chemical manufacturing, and pharmaceuticals rely on catalytic technology. Given the growing issues of energy depletion and environmental concerns, the development of low-cost and environmentally friendly catalytic technologies is imperative.
Photocatalysis
Photocatalysis employs photo-generated charge carriers to catalyze reactions. The mechanism and pathway differ from thermocatalysis. Photocatalytic reactions are conducted under mild conditions and are easy to operate. Compared to the history of traditional catalysis that spans over three centuries, photocatalysis is a relatively young and novel type of catalytic reaction.
As a technology that converts abundant solar energy into chemical energy, the history of photocatalysis can be traced back to 1972 when Fujishima and Honda[2] first reported that illumination of an n-type semiconductor TiO₂ electrode led to the decomposition of water into hydrogen and oxygen gases. This discovery ignited academic interest in photocatalysis, making it a hot research topic. Over the years, photocatalysis has found applications in various fields such as water splitting for H₂ production[3,4], CO₂ reduction[5,6], degradation of pollutants in wastewater and air[7,8], and artificial photosynthesis[9,10].
Photothermal Catalysis
In recent years, along with the deepening of catalysis research and the emergence of interdisciplinary intersections, the combination of multiple methods, such as thermocatalysis, photocatalysis, and electrocatalysis, has gained attention among researchers. Photothermal catalysis, proposed by scholars in recent years, is a novel technique that integrates photocatalysis and thermocatalysis into a unified process. Photothermal catalysis can enhance the efficiency of catalytic reactions while converting low-density solar energy into high-density chemical energy.
Generally, if a reaction involves transformations using light, heat, and catalysis, it can be regarded as photothermal catalysis.
Photothermal catalysis can be divided into three major categories:
① Thermally-assisted photocatalytic reactions, mainly driven by light with the catalyst itself not possessing thermocatalytic activity. Thermal energy assists in further reducing the apparent activity of photocatalysis;
② Photo-assisted thermocatalytic reactions, where thermal energy is the primary driving force of the entire reaction, while light radiation mainly serves to elevate local temperatures, potentially coexisting with photochemical effects;
③ Photothermal-coupled catalysis, where heat released from photothermal effects can enhance the reaction process, while photochemical effects boost apparent activity. The synergistic effects of thermochemistry and photochemistry exceed the sum of the activities of photocatalysis and thermocatalysis.
The above section is translated and summarized by the author based on reference materials. The author's expertise is limited, so if there are any errors, please kindly correct them!
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