Molecular Chemical Engines: Pseudo-Static Processes and the Mechanism of Energy Transduction

TL;DR

This paper introduces a theoretical model of a molecular chemical engine that converts chemical energy into mechanical work, analyzing work output during pseudo-static processes and exploring the energy transduction mechanism.

Contribution

It presents a simple, analytically solvable model accounting for binding/unbinding of molecules, and examines work limits and energy transduction in pseudo-static processes.

Findings

Work can exceed thermodynamic limits in single cycles by chance.

Average work does not surpass the second law limit.

Maximum work occurs in reversible processes.

Abstract

We propose a simple theoretical model for a molecular chemical engine that catalyzes a chemical reaction and converts the free energy released by the reaction into mechanical work. Binding and unbinding processes of reactant and product molecules to and from the engine are explicitly taken into account. The work delivered by the engine is calculated analytically for infinitely slow (``pseudo-static'') processes, which can be reversible (quasi-static) or irreversible, controlled by an external agent. It is shown that the work larger than the maximum value limited by the second law of thermodynamics can be obtained in a single cycle of operation by chance, although the statistical average of the work never exceeds this limit and the maximum work is delivered if the process is reversible. The mechanism of the energy transductionis also discussed.