Testing novel multicomposite materials for electromethanogenesis

Electromethanogenesis is an innovative technology that uses a microbial electrochemical system to produce methane from CO2, in a power-to-gas (BEP2G) concept. The results of experimental tests of new and cost-effective carbonaceous materials for electrode are presented here. The study aims at optimizing electromethanogenesis processes at laboratory level in mesothermic condition. As part of the experiments, hydrogenotrophic microorganisms (Family Metanobacteriaceae of Archaea domains) were selected from a mixed consortium taken from a biogas digestate and inoculated in double-chamber bioelectrochemical systems. The maximum amount of methane produced was 0.3 - 0.8 mol/m2g (normalized to the cathode area) with carbon cloth electrodes. Aiming at improving the methane productivity, innovative materials for the electrodes were now studied, creating porous high-surface composites, and studying nitrogen carbons doped with Cu and hydroxyapatite (Multicomposite Cu@/HAP/C), as chemical catalysts for CO2 reduction (CO2RR). The description of the procedure for the Multicomposite Cu@/HAP/C production is reported in detail.

Single-Chamber Microbial Fuel Cell with Multiple Plates of Bamboo Charcoal Anode: Performance Evaluation

In this study, three single-chamber microbial fuel cells (MFCs), each having Pt-coated carbon cloth as a cathode and four bamboo charcoal (BC) plates as an anode, were run in a fed-batch mode, individually and in series. Simulated potato-processing wastewater was used as a substrate for supporting the growth of a mixed bacterial culture. The maximum power output increased from 0.386 mW with one MFC to 1.047 mW with three MFCs connected in series. The maximum power density, however, decreased from 576 mW/m2 (normalized to the cathode area) with one MFC to 520 mW/m2 with three MFCs in series. The experimental results showed that power can be increased by connecting the MFCs in series; however, choosing low resistance BC is crucial for increasing power density.

Determining the current profile along the anode-cathode line in Cu/Ni electrolyte by logger pro

In electroplating, the broad role of cathode and anode is often neglected. This study aims to simultaneously prove the electric current in the three pairs of probes in the cathode-anode direction. It also describes the effect of variations in the anode-cathode area ratio. This result proves that the greater the ratio, the greater the current density in all pairs of probes. Data retrieval used a current sensor current probe DCP-BTA Vernier displayed on a computer screen with the help of Logger Pro software. The results in the study show that the current at every point in the measurement has a less identical graph. In electroplating, nickel (Ni)-1 has a relatively constant amplitude than nickel (Ni)-2. The variation of the anode area ratio at the first nickel (Ni) is 1: 0.821. The ratio of the anode area to the second nickel (Ni) is 1: 0.343. From the analysis results, the first nickel (Ni) has a relatively constant amplitude compared to the second nickel (Ni).

Effect of Alternating Stray Current Density on Corrosion Behavior of X80 Steel under Disbonded Coating

In this paper, the effect of alternating stray current (AC) density on the corrosion behavior of X80 steel under disbonded coating was studied by electrochemical methods, wire beam electrode (WBE) technology, and surface observation technology. The results showed that under the interference of different AC densities, the corrosion potential of X80 steel under disbonded coating underwent negative deviation, and the degree of negative deviation increased with the increase of AC density. The corrosion current density of X80 steel under disbonded coating with the action of 0~100 A/m2 AC density had few differences. While the corrosion current density of X80 steel with the action of 200~300 A/m2 AC density increased and the corrosion current density was higher than that under low AC density. The cathode area of the wire beam electrode under disbonded coating is mainly distributed outside and the edge of the gap between disbonded coating and X80 steel, while the anode area is mainly distributed inside the gap.

Manufacturing fine graphite powder with AC electric synthesis

There is presented a technology for manufacturing fine powder of graphite of GE type by means of synthesis. A device with the separation of anode and cathode area by means of Dacron diaphragm use is described. Basic elements of the installation are a stainless steel cathode and a graphite anode submerged into aqueous solution (electrolyte). As a result of the experiment there is obtained fine powder with an average graphite particle size of 4mkm.

Corrosion of Steel Rebars in Anoxic Environments. Part II: Pit Growth Rate and Mechanical Strength

Reinforced concrete may corrode in anoxic environments such as offshore structures. Under such conditions the reinforcement fails to passivate completely, irrespective of chloride content, and the corrosion taking place locally induces the growth of discrete pits. This study characterised such pits and simulated their growth from experimentally determined electrochemical parameters. Pit morphology was assessed with an optical profilometer. A finite element model was developed to simulate pit growth based on electrochemical parameters for different cathode areas. The model was able to predict long-term pit growth by deformed geometry set up. Simulations showed that pit growth-related corrosion tends to maximise as cathode area declines, which lower the pitting factor. The mechanical strength developed by the passive and prestressed rebar throughout its service life was also estimated. Passive rebar strength may drop by nearly 20% over 100 years, whilst in the presence of cracking from the base of the pit steel strength may decline by over 40%.

Research on the Metal Corrosion Process in the Sea Mud/Seawater/Atmosphere Interface Zone

Corrosion in the interface zone is a complicated local corrosion phenomenon. The conventional single-electrode method finds it difficult to obtain the kinetic information of corrosion occurrence and development process. In this paper, metal corrosion was studied by Wire Beam Electrode (WBE) technology on the interfaces of sea mud/seawater and seawater/atmosphere. The study found that the metal corrosion in the interface is a process of coupling a dual corrosion cell into a single corrosion cell. Initially, a corrosion cell is formed with the seawater/atmosphere interface acting as the cathode and the upper part of the metal in the seawater area as the anode. This is due to the oxygen concentration cell caused by the waterline effect. The cathode area is always enriched near the seawater/atmosphere interface. The lower part of the metal in the seawater area and the metal in the sea mud area are the anode and the cathode, respectively, of another corrosion cell. Along with the immersion time, the anodic area of the first corrosion cell gradually extends to the lower part of the metal in the seawater zone and finally the sea mud zone, resulting in the disappearance of the second corrosion cell. In the single corrosion cell stage, the seawater/atmosphere interface is the cathode area; the seawater area and the sea mud area are the anode areas, and the electrode adjacent to the cathode area becomes the anode area with the largest current density. During the whole experiment, the sea mud zone is a process of polarity transition from the cathode zone to the anode zone, and finally forms the anode zone of the whole electrode together with the anode zone in the sea zone.

Biochar-Terracotta Conductive Composites: New Design for Bioelectrochemical Systems

Research in the field of bioelectrochemical systems is addressing the need to improve components and reduce their costs in the perspective of their large-scale application. In this view, innovative solid separators of electrodes, made of biochar and terracotta, are investigated. Biochar-based composites are produced from giant cane (Arundo Donax L.). Two different types of composite are used in this experiment: composite A, produced by pyrolysis of crushed chipping of A.donax L. mixed clay; and composite B, produced by pyrolysis of already-pyrolyzed giant cane (biochar) mixed with clay. Electrical resistivity, electrical capacity, porosity, water retention, and water leaching of the two composites types (A and B) with 1, 5, 10, 15, 20, and 30 mass percentages of carbon (w/w) are characterized and compared. Less than 1 kΩ cm of electrical resistance is obtained for composite A with a carbon content greater than 10%, while physical and electrical performances of composite B do not significantly change. SEM micrographs and 3D microcomputed tomography of different composite materials are provided, demonstrating a different matrix structure of carbon in the terracotta matrix. The possibility of suitably decreasing electric resistance and increasing water retention/leaching of composite A opens the way for a new class of resistive materials that can be simultaneously used as electrolytic separators and as external electric circuits, allowing a compact microbial fuel cell design. A proof of concept of such an MFC design was provided for different tested composites. Although all the anolytes become anaerobic, only the MFCs equipped with the composite A30% were able to produce power, reaching the maximum power peak in correspondence to resistance of about 1 kΩ. The low, but significant, produced power (about 40 mW m−2, cathode area) confirm that the proposed solution is particularly suitable for nutrient recovery and environment pollution bioremediation, where energy harvesting is not requested.

Revealing the growth kinetics of atmospheric corrosion pitting in aluminum via in situ microtomography

Understanding the mechanistic relationship between the environment, microstructure, and local kinetics of atmospheric corrosion damage remains a central challenge. To address this challenge, this study used laboratory-based X-ray tomography to directly observe attack in-operando over an extended period, enabling insights into the evolving growth kinetics and morphology of individual pits over months of exposure. Damage progression associated with nine pits in a 99.9% pure aluminum wire exposed to chloride salts in humid air was characterized. Most pits grew at a nominally linear rate up until pit death, which occurred within 12–24 h of nucleation. Exceptions to this were observed, with three pits exhibiting bimodal growth kinetics and growing for 40 or more hours. This was explained by secondary droplets that formed near the pits, increasing the cathode area. A corrosion-driven drying mechanism likely contributed to pit death in both cases. Pits first grew into the material followed by lateral expansion.

Contact Glow Discharge Electrolysis: Effect of Electrolyte Conductivity on Discharge Voltage

Contact glow discharge electrolysis (CGDE) can be exploited in environmental chemistry for the degradation of pollutants in wastewater. This study focuses on the employment of cheap materials (e.g., steel and tungsten) as electrodes for experiments of CGDE conducted in electrochemical cells with variable electrolytic composition. A clear correlation between breakdown voltage (VB)/discharge (or midpoint) voltage (VD) and the conductivity of the electrolyte is shown. Regardless of the chemical nature of the ionogenic species (acid, base or salt), the higher the conductivity of the solution, the lower the applied potential required for the onset of the glow discharge. Concerning practical application, these salts could be added to poorly conductive wastewaters to increase their conductivity and thus reduce the ignition potential necessary for the development of the CGDE. Such an effect could render the process of chemical waste disposal from wastewaters more economical. Moreover, it is evidenced that both VB and VD are practically independent on the ratio anode area to cathode area if highly conductive solutions are employed.