Impact of electrode micro- and nano-scale topography on the formation and performance of microbial electrodes

Abstract

From a fundamental standpoint, microbial electrochemistry is unravelling a thrilling link between life and materials. Technically, it may be the source of a large number of new processes such as microbial fuel cells for powering remote sensors, autonomous sensors, microbial electrolysers and equipment for effluent treatment. Microbial electron transfers are also involved in many natural processes such as biocorrosion. In these contexts, a huge number of studies have dealt with the impact of electrode materials, coatings and surface functionalizations but very few have focused on the effect of the surface topography, although it has often been pointed out as a key parameter impacting the performance of electroactive biofilms. The first part of the review gives an overview of the influence of electrode topography on abiotic electrochemical reactions. The second part recalls some basics of the effect of surface topography on bacterial adhesion and biofilm formation, in a broad domain reaching beyond the context of electroactivity. On these well-established bases, the effect of surface topography is reviewed and analysed in the field of electroactive biofilms. General trends are extracted and fundamental questions are pointed out, which should be addressed to boost future research endeavours. The objective is to provide basic guidelines useful to the widest possible range of research communities so that they can exploit surface topography as a powerful lever to improve, or to mitigate in the case of biocorrosion for instance, the performance of electrode/biofilm interfaces.

Effect of pore size on the current produced by 3-dimensional porous microbial anodes: A critical review

“…With pore sizes around 1 µm and less, the main advantage of the 3D porous electrodes would be lost because biofilm would grow only on the outer surface. Nevertheless, it cannot be ruled out that such small pore sizes may promote cell anchoring and biofilm development by creating surface roughness (Champigneux et al, 2018a). Regardless of the intended application, the objective is most often to increase the process rate, i.e.…”

“…The large internal area of the porous structure is not exploited. Actually, porosity acts in the same manner as surface topography could (Champigneux et al, 2018a).…”

“…The trends established here can be used to optimize the macro-/micro-porosity. In contrast, it is difficult to establish clear trends to guide surface nano-structuring, which remains a worthwhile research objective (Champigneux et al, 2018a).…”

Benchmarking of Industrial Synthetic Graphite Grades, Carbon Felt, and Carbon Cloth as Cost-Efficient Bioanode Materials for Domestic Wastewater Fed Microbial Electrolysis Cells

“…In general, surfaces with S a lower than 0.8 µm are considered as "hygienic" surface and are not suitable for microbial growth (Flint et al, 2000). Moreover, S a values in the range of 1-10 µm are ideal for biofilm adhesion (Pons et al, 2011;Kano et al, 2012;Santoro et al, 2014;Champigneux et al, 2018). Indeed, bacteria particularly prefer rough areas and surface deformations, which size range is of the same order of magnitude as the size of the bacteria, i.e., in the order of a few micrometers.…”

Effect of surface roughness, porosity and roughened micro-pillar structures on the early formation of microbial anodes

“…In this very broad context, the research community is still facing an important gap in basic knowledge when the objective is to control the electrode/bacteria interface. The predominant role of electrode topography has been pointed out in many studies [18][19][20][21][22][23][24][25][26] and in a recent review article [27], but controversial results have been reported. For instance, surface roughness has sometimes been reported as the main parameter that impacts the current density produced by microbial anodes, being even more important than the anode material itself [28].…”