They discovered that the Pt-HEAs' surfaces performed better in ORR compared to surfaces made of a platinum-cobalt alloy. Using advanced imaging techniques, the group examined the atomic-level structure of the Pt-HEAs' surfaces and studied their ORR properties. "This produced a model surface for studying a specific reaction called the oxygen reduction reaction (ORR)." "In our study we made thin layers of an alloy called a Cantor alloy, which contains a mix of elements (Cr-Mn-Fe-Co-Ni), on platinum (Pt) substrates," explains Toshimasa Wadayama, co-author of the paper and a professor at Tohoku University's Graduate School of Environmental Studies. Their breakthrough was reported in the journal Nature Communications on July 26, 2023. Now, a collaborative research team has created a new experimental platform that enables the control of the atomic-level structure of HEAs' surfaces and the ability to test their catalytic properties. Hence why researchers are seeking to understand the correlation between the atomic arrangement and the catalytic properties exhibited by HEAs. But unravelling this complexity is crucial, since the surface properties of materials often dictate their catalytic activity. It is an exothermic reaction, therefore, favours the process, but randomness factor opposes the reaction.Īs the reaction takes place, the energy factor must be greater than the randomness factor.Because they are made up of differing constituent elements, HEAs' atomic-level surface designs can be complex. (b) The reaction between hydrogen and oxygen to form water. Since the process is known to take place, randomness factor must be greater than energy factor. Evaporation of water is endothermic, therefore, energy factor opposes the process. When the two tendencies act in the opposite direction, the tendency with the greater magnitude determines whether the process is feasible or not. (iii) the driving force is the resultant of the magnitude of the two tendencies. (ii) the two tendencies may work in the same direction or opposite direction in a process and (i) the two tendencies act independent of each other, The overall tendency of a process to take place by itself is called the driving force. (ii) the tendency to acquire a state of maximum randomness or disorder. (i) the tendency to acquire a state of minimum energy, and The overall tendency of a process to occur can be expressed on the resultant of two tendencies namely: Thus, this concept of entropy (measure of randomness) has led to the conclusion that all substances in their normal crystalline state at absolute zero temperature would be in the condition of maximum orderly arrangement, because all motion has essentially ceased at ‘0 K.’ In other words, entropy of a substance at 0 K is minimum. When two gases are mixed, the molecules of the gases intermix to achieve more randomness. The process of vaporisation produces an increase in randomness in the distribution of molecules, hence an increase in entropy. For example, when a solid changes to a liquid, an increase in entropy takes place, because with the breaking of the orderly arrangement of the molecules in the crystal to the less orderly liquid state, the randomness increases. Conversely, if the change is one in which there is an increase in orderliness, there is a decrease in entropy. Physical significance: Entropy has been regarded as a measure of disorder or randomness of a system. Thus when a system goes from a more orderly to less orderly state, there is an increase in its randomness and hence entropy of the system increases.
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