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Electrocatalyst-coated metallic electrodes for electrochemical flow reactors have many applications in electrosynthesis, environmental remediation and energy conversion. This work presents novel nickel-coated titanium-alloy electrodes produced by means of direct metal laser sintering and constant current electrodeposition in an additive-free Wood's nickel strike then a Watts nickel bath. Several 3D porous architectures were created in Ti-6Al-4 V alloy and coated, their digital design being the subject of previous work. Nickel coatings were macroscopically uniform and adherent with a thickness up to 5.8 µm, depending on the surface area of the electrodes. The morphology of nickel was cauliflower-like, with crystallisation growth occurring as spherical grains, as typically found for deposits from pH buffered Watts baths. Some degree of coating porosity was observed at electrodes of large surface area, indicating the need for longer deposition times. The results open the path for further optimisation of electrodeposition parameters and the development of bath additives to tailor deposit properties. [ABSTRACT FROM AUTHOR]

Aiming to demonstrate the importance and facility of characterising the reaction environment in new commercial laboratory-scale flow cells, fluid flow, pressure drop and space averaged mass transport coefficient were studied in the C-Flow® Lab 5 × 5 cell. A flow-by configuration with smooth, planar electrodes in a rectangular channel was used. Electrolyte mean linear velocities of 2 to 10 cm s−1 past the electrode surface and channel Reynolds numbers of 53 to 265 were considered. The effect of a turbulence promoter next to the working electrode was evaluated. Flow distribution was explored by a qualitative flow visualization study, while the relevance of pressure drop was shown by measurements over the flow channel and the whole cell as a function of mean linear velocity. The electrochemical performance was quantified from the limiting current, permitting the determination of the mass transport coefficient at the electrodes over the same range of flow rates. Reactant conversion in the batch recirculation mode and normalised space velocity were predicted from the electrochemical plug flow reactor design equation. Results were compared to well-characterised electrochemical flow reactors found in the literature. The significance of characterisation techniques and basic reactor models during the development of new processes is emphasised. [ABSTRACT FROM AUTHOR]

Electrochemical cells continue to be important in the synthesis and processing of commodity and speciality chemicals, environmental remediation, energy conversion and electrodeposition. A current challenge is an increasing need to achieve a high performance from cells which can be easily designed, manufactured or modified. Conventional manufacturing has involved machining of cast and extruded materials in a mechanical engineering workshop, which can involve delays, the need for skilled specialists and considerable costs. Increasingly, the benefits of fast prototyping as a route to manufacture are being realised. Modern approaches to detailed imaging of structures (e.g. by computed tomography) can be combined with on-screen, digital design (via computer software suites), followed by modification then data export to a 3D printer. In this fashion, a fast, flexible, cost effective and attractive route to manufacture of prototype electrodes and cell bodies can be realised. This review paper demonstrates the success of a design-image-manufacture cycle to realise polymeric electrochemical flow cell compartments and electrodes. Future developments are suggested, with 3D printing likely to offer creative solutions in many surface finishing applications. [ABSTRACT FROM AUTHOR]

The features of the plane parallel geometry are reviewed since this cell geometry occupies a prominent position, both in the laboratory and in industry. The simple parallel plate can be enhanced by inclusion of porous, 3D electrodes, structured surfaces and bipolar electrical connections, with adequate attention to the reaction environment. Unit cells are often arranged in a modular, filterpress format. Scale-up is achieved by increasing the size of each electrode, the number of electrodes in a stack or the number of stacks in a system. The use of turbulence promoters in the flow channel, textured (including nanostructured) and porous electrodes as well as cell division by an ion exchange membrane can considerably widen the scope of the plane parallel geometry. Features of plane parallel cell designs are illustrated by selected examples from our laboratories and industry, including a fuel cell, an electrosynthesis cell and hybrid redox flow cells for energy storage. Recent trends include the development of microflow cells for electrosynthesis, 3D printing of fast prototype cells and a range of computational models to simulate reaction environment and rationalise performance. Future research needs are highlighted. [ABSTRACT FROM AUTHOR]

The versatility and convenience of 3D printing can be used to produce tailored metal mesh electrodes, which offer a high volumetric area and good gas release properties for applications in electrochemical technology. In this work, a titanium mesh with 20 ppi triangular pores was designed and then manufactured by 3D printing. A thin coating of platinum with strong adhesion was then applied by electrodeposition in a solution of hexachloroplatinic acid in HCl at 90°C. For this, a current of 0.1 A, corresponding to a current density of 0.92 mA cm−2 was applied for 60 min to the work piece, which was previously etched in 10% (w/v) oxalic acid at 80°C. Compact, adherent and silver-grey platinum deposits, 0.16 µm average thickness and 0.33 mg cm−2 Pt loading were obtained. The product can be used as an inert anode in nickel plating baths and as a porous electrode in organic electrosynthesis or cerium-based flow batteries. [ABSTRACT FROM AUTHOR]