Electrocatalytic Mechanism Involving Michaelis-Menten Kinetics at the Preparative Scale: Theory and Applicability to Photocurrents from a Photosynthetic Algae Suspension With Quinones

In the past years, many strategies were implemented to take benefits from oxygenic photosynthesis to harvest photosynthetic electrons and produce a significant photocurrent. Therefore, electrochemical tools were considered and globally relied on the electron transfer(s) between the photosynthetic chain and a collecting electrode. In this context, we recently reported the implementation of an electrochemical set-up at the preparative scale to produce photocurrents from a Chlamydomonas reinhardtii algae suspension with an appropriate mediator (2,6-DCBQ) and a carbon gauze as the working electrode. In the present work, we wish to describe a mathematical modeling of the recorded photocurrents to better understand the effects of the experimental conditions on the photosynthetic electrons extraction. In that way, we established a general model of an electrocatalytic mechanism at the preparative scale (i.e. assuming a homogenous bulk solution at any time and a constant diffusion layer, both assumptions are being valid under forced convection) in which the chemical step involves a Michaelis-Menten like behavior. Dependences of transient and steady-state corresponding currents were analyzed as a function of different parameters by the mean of zone diagrams. Such a model was tested to our experimental data related to photosynthesis. The corresponding results suggest that competitive pathways beyond the only photosynthetic harvesting should be taken into account.