Is maximising current density always the optimum strategy in electrolyser design for electrochemical CO2 conversion to chemicals?

Electrochemical conversion of CO2 to chemicals and fuels can potentially play a role in reducing CO2 emissions from industrial processes and providing non-fossil fuel routes to important chemical feedstocks. Most of the recent research on electrocatalysts for CO2 reduction (CO2R) focuses on achieving maximum selectivity for desired products at the highest possible current density. This approach assumes that maximising current density leads to the lowest cost of CO2R (e.g. $·kg-1 CO2 converted) because it requires the lowest catalyst loadings and electrode area per kg of CO2 treated and thus minimising the electrolyser equipment cost. Using a techno-economic analysis (TEA) model with experimental data from a two-cell vapor fed electrolyser, we show this assumption is not valid for CO2 conversion to CO if the process model accounts for relationships between current density, selectivity, cell voltage, ohmic losses, and product separation costs. Instead, our model predicts the lowest CO production costs at current densities from 500 – 700 A·m-2. At current densities above 1000 A·m-2, growing ohmic losses in the electrolyser lead to increasing power costs that become much larger than any capital savings related to reduced electrode area at the higher current density. Further, we investigate different opportunities that could bring down the CO production cost, however, in all the cases, the lowest CO production cost was found at current densities between 600 – 1400 A·m-2. This work also provides insights that can help identify feasible design spaces for both catalysts and electrolysers to develop CO2 conversion technologies that could soon compete on a cost basis with the natural reforming technologies to produce CO (0.60 $·kg-1 market price).

Design of the MIDES plant

This chapter presents the full design of two microbial desalination cells (MDCs) at pilot-plant scale from the MIDES project. The final MDC pilot unit design was based on the knowledge gained through up scaling of the MDC from lab- to prepilot scale. The MDC pilot plant consists of one stack of 15 MDC pilot units with 0.4 m2 electrode area. This chapter also presents the piping and instrumentation diagram (P&ID) and layout of the MDC pilot plant. The MIDES pilot plants are comprised of an MDC pilot plant housed in a 40-ft container with the rest of the peripheral elements. Finally, this chapter presents the improvement made from the first to the second MDC stack in terms of stability and the chemical compatibility of the end plates.

Common-Mode Voltage Reduction in Capacitive Sensing of Biosignal Using Capacitive Grounding and DRL Electrode

A capacitive measurement of the biosignals is a very comfortable and unobtrusive way suitable for long-term and wearable monitoring of health conditions. This type of sensing is very susceptible to noise from the surroundings. One of the main noise sources is power-line noise, which acts as a common-mode voltage at the input terminals of the acquisition unit. The origin and methods of noise reduction are described on electric models. Two methods of noise removal are modeled and experimentally verified in the paper. The first method uses a passive capacitive grounding electrode, and the second uses an active capacitive Driven Right Leg (DRL) electrode. The effect of grounding electrode size on noise suppression is experimentally investigated. The increasing electrode area reduces power-line noise: the power of power-line frequency within the measured signal is 70.96 dB, 59.13 dB, and 43.44 dB for a grounding electrode area of 1650 cm2, 3300 cm2, and 4950 cm2, respectively. The capacitive DRL electrode shows better efficiency in common-mode noise rejection than the grounding electrode. When using an electrode area of 1650 cm2, the DRL achieved 46.3 dB better attenuation than the grounding electrode at power-line frequency. In contrast to the grounding electrode, the DRL electrode reduces a capacitive measurement system’s financial costs due to the smaller electrode area made of the costly conductive textile.

Influence of the Catalyst Layer Structure Formed by Inkjet Coating Printer on PEFC Performance

In this study, we investigated the influence of the Catalyst-Layer (CL) structure on Polymer Electrolyte Fuel Cell (PEFC) performance using an inkjet coating printer, and we especially focused on the CL thickness and the electrode area. In order to evaluate the influence of CL thickness, we prepared four Membrane Electrode Assemblies (MEAs), which have one, four, five and six CLs, respectively, and evaluated it by an overpotential analysis. As a result, the overpotentials of an activation and a diffusion increased with the increase of thickness of CL. From Energy Dispersive X-ray spectroscopy (EDX) analysis, because platinum twines most ionomers and precipitates, the CL separates into a layer of platinum with a big grain aggregate ionomer and the mixing layer of platinum and ionomer during the catalyst ink drying process. Consequently, the activation overpotential increased because the three-phase interface was not able to be formed sufficiently. The gas diffusivity of the multilayer catalyst electrode was worse than that of a single layer MEA. The influence of the electrode area was examined by two MEAs with 1 and 9 cm2 of electrode area. As a result, the diffusion overpotential of 9 cm2 MEA was worse than 1 cm2 MEA. The generated condensate was multiplied and moved to the downstream side, and thereafter it caused the flooding/plugging phenomena.

Electric modulation of conduction in MAPbBr3 single crystals

The resistive switching (RS) mechanism of hybrid organic-inorganic perovskites has not been clearly understood until now. A switchable diode-like RS behavior in MAPbBr3 single crystals using Au (or Pt) symmetric electrodes is reported. Both the high resistance state (HRS) and low resistance state (LRS) are electrode-area dependent and light responsive. We propose an electric-field-driven inner p-n junction accompanied by a trap-controlled space-charge-limited conduction (SCLC) conduction mechanism to explain this switchable diode-like RS behavior in MAPbBr3 single crystals.

A heat-melt adhesive-assisted transferable electrode films

This report is the first on heat-assisted transferable battery components, enabling manufacturing batteries on non-planer surfaces such as a curved surface and an edge. The transferrable battery components were composed of two layers: a cathode or an anode and a conductive heal-melt adhesive layer on a silicone-based flexible supporting paper. These mechanically-durable, flexible components enabled conformable adhesion even on curved surfaces and substrate edges. As a model battery, the manganese dioxide-zinc system was constructed on a curved surface using transfer techniques and showed a practical capacity of 1.8 mAh cm−2 per unit electrode area. These transferable electrodes allow arbitrary design of batteries according to the power consumption of IoT devices to be fabricated on unreported geometries where has been considered as a dead space.

Potensiometric of Struvite (MgNH4PO4.6H2O) Formation System from Biogas Waste in Electrolysis Cells

Struvite is a yellowish white or brownish yellow crystal. Struvite occurs in an alkaline environment. The reaction that occurs is the reduction of H+ and at the anode is H2O oxidation. The purpose of this study was to determine the maximum potential conditions of deposition of struvite which was contained in biogas waste by electrolysis process and to improve the quality of struvite fertilizer. The method was carried out with the electrolysis time condition of 30 minutes where the electrical voltages used were 1V, 3V, 5V, 7V, and 9V and the size of the electrodes used were 30 cm, 36 cm, 50 cm, 60 cm, 70 cm. From the research that has been done, it could be seen that the struvite formed was very small, the best conditions in this study at 5V voltage and 36 cm electrode area with a yield of 28.8%.

The Identification of Electrolyte Property of Humus-Contained Andosol Soil Using Cu-Zn Electrodes

<p><em>This study investigated the electrolyte property of humus-contained andosol soil using Volta cell. The electrodes that are used were Cu and Zn for cathode and anode, respectively. This research was done by varying electrode area and distance between Cu and Zn electrodes. The varied electrode area was 20, 30, and 40 cm², whereas the electrode distance was 3, 4, and 5 cm. Then, the current and voltage profiles of Volta cell system were measured using a digital multimeter. The result showed that humus-contained andosol soil has an electrolyte property. Electrolyte property of andosol soil might be due to the humus substance that has a high cationic-exchange capacity. Besides, it showed that the increase of the electrode area, the current and voltage were increased gradually. In contrast, the increase in current and voltage could be found by the decrease of electrode distance. In addition, the use of 24-Volta cells system enhancing current and voltage compared to a single cell. It suggests that the increase of current and voltage was relatively proportional to the number of Volta cell. Therefore, this research can be a reference for the identification of electrolyte property of natural or waste materials.</em></p>