  The propulsion of active particles by self-diffusiophoresis is driven by
asymmetric catalytic reactions on the particle surface that generate a
mechanochemical coupling between the fluid velocity and the concentration
fields of fuel and product in the surrounding solution. Because of thermal and
molecular fluctuations in the solution, the motion of micrometric or
submicrometric active particles is stochastic. Coupled Langevin equations
describing the translation, rotation, and reaction of such active particles are
deduced from fluctuating chemohydrodynamics and fluctuating boundary conditions
at the interface between the fluid and the particle. These equations are
consistent with microreversibility and the Onsager-Casimir reciprocal relations
between affinities and currents, and provide a thermodynamically consistent
basis for the investigation of the dynamics of active particles propelled by
diffusiophoretic mechanisms.
