Review—The Design, Performance and Continuing Development of Electrochemical Reactors for Clean Electrosynthesis

Abstract

A critical review of classical and improved electrodes, electrocatalysts and reactors is provided. The principles governing the selection of electrochemical flow reactor or progression of a particular design for laboratory or pilot scale are reviewed integrating the principles of electrochemistry and electrochemical engineering with practical aspects. The required performance, ease of assembly, maintenance schedule and scale-up plans must be incorporated. Reactor designs can be enhanced by decorating their surfaces with nanostructured electrocatalysts. The simple parallel plate geometry design, often in modular, filter-press format, occupies a prominent position, both in the laboratory and in industry and may incorporates porous, 3D or structured electrode surfaces and bipolar electrical connections considering the reaction environment, especially potential- and current-distributions, uniformity of flow, mass transport rates, electrode activity, side reactions and current leakage. Specialised electrode geometries include capillary gap and thin film cells, rotating cylinder electrodes, 3-D porous electrodes, fluidised bed electrodes and bipolar trickle tower reactors. Applications span inorganic, organic electrosynthesis and environmental remediation. Recent developments in cell design: 3D printing, nanostructured, templating 3D porous electrodes, microchannel flow, combinatorial electrocatalyst studies, bioelectrodes and computational modelling. Figures of merit describing electrochemical reactor performance and their use are illustrated. Future research and development needs are suggested.

Hydrophobic thiol coatings to facilitate a triphasic interface for carbon dioxide reduction to ethylene at gas diffusion electrodes

“…18,19 In all cases, the highest current densities are invariably recorded at gas diffusion electrodes (GDEs), which ow CO 2 through a porous support towards the catalyst-electrolyte interface. 20 This keeps CO 2 mass transport in the gas phase and helps to negate issues surrounding low CO 2 solubility to give a much faster rate of reaction. 21 Much of the discussion around CO 2 RR activity centres on the triphasic interface, where gaseous CO 2 reacts with a liquid electrolyte at a solid catalyst surface.…”

Electrochemical Reduction of Carbon Dioxide on 3D Printed Electrodes

“…functionalities for reaction mechanistic studies, [34] spectroelectrochemical analysis, [35,36] electroanalytical sensing [37][38][39][40][41][42] or organic electrosynthesis. [43] Recent achievements in the preparation of thermoplastic composites involving conductive additives allowed FDM 3DP to be utilized to manufacture electrodes. The seminal work of Rymansaib et al [40] demonstrated that polystyrene/graphite/carbon nanofiber composite may be used to print electrodes applicable in electroanalytical sensing.…”

A Facile Method to Realize Oxygen Reduction at the Hydrogen Evolution Cathode of an Electrolytic Cell for Energy-Efficient Electrooxidation

“…Electrochemical oxidation is an important part of electrolysis and electrosynthesis, both of which use electrons as reagents and control the rate and direction of reactions by adjusting the electrode potential, thus constituting an effective means of green chemistry [ 1 , 2 , 3 , 4 , 5 , 6 ]. Electrochemical oxidation, realized through direct electron transfer and/or by reducing the oxidants generated in situ, can be used to produce a variety of inorganic and organic chemicals, including chlorine gas [ 7 ], potassium permanganate [ 8 ], ammonium persulfate [ 9 ], ozone [ 10 ], benzaldehyde [ 11 ], trifluoroacetic acid [ 12 ], p-anisaldehyde [ 11 ], etc.…”