Biomimetic Artificial Proton Channels

Abstract

One of the most common biochemical processes is the proton transfer through the cell membranes, having significant physiological functions in living organisms. The proton translocation mechanism has been extensively studied; however, mechanistic details of this transport are still needed. During the last decades, the field of artificial proton channels has been in continuous growth, and understanding the phenomena of how confined water and channel components mediate proton dynamics is very important. Thus, proton transfer continues to be an active area of experimental and theoretical investigations, and acquiring insights into the proton transfer mechanism is important as this enlightenment will provide direct applications in several fields. In this review, we present an overview of the development of various artificial proton channels, focusing mostly on their design, self-assembly behavior, proton transport activity performed on bilayer membranes, and comparison with protein proton channels. In the end, we discuss their potential applications as well as future development and perspectives.

Proton Relay for the Rate Enhancement of Electrochemical Hydrogen Reactions at Heterogeneous Interfaces

“…Proton transfer plays a critical role in diverse chemical, biochemical, and electrochemical processes. − The hydrogenase enzyme, microalgae, and bacteria achieve reversible proton-coupled chemical transformations by precisely controlling proton movement to and from the active sites of, for example, iron or nickel complexes with organic ligands (e.g., porphyrins or polypyridine). − To mimic the function of how natural systems manipulate proton transfer, many artificial molecular electrocatalysts have been designed and synthesized in which certain basic pendant groups function as proton relays to promote proton transfer and improve reaction kinetics. − Recently, significant improvement of ORR kinetics on Pt and Au electrocatalysts has been demonstrated through tuning proton transfer by modifying electrodes with protonic ionic liquids, while ORR reaction pathways on a heterogenized molecular Cu electrocatalyst can be controlled through a lipid-bound proton carrier. , Progress has been made in understanding the critical role of protons in the electrochemical transformation of organic molecules (formic acid, alcohol, nitrobenzene) and hydrogen , at heterogeneous interfaces. Molecular control of heterogeneous electrocatalysis has been achieved through the graphite-conjugated acid approach. , Progress has also been made in understanding how noncovalent interactions affect heterogeneous electrocatalysis through tuning electrolyte composition. − We, therefore, hypothesize that a proton relay can be built in heterogeneous electrocatalysts to more efficiently promote proton transfer and improve electrochemical reaction kinetics for which a proton is involved in the elementary step of the specific reaction (i.e., H + -containing reactions)Scheme .…”