Evaluation of Electrosorption Process for Phosphate and Nitrate Removal from Wastewater

The present work is dedicated to the preparation and characterization of carbon-based electrodes for the removal of phosphates and nitrate ions from wastewater by CDI method. Carbons obtained from the pyrolysis were used to prepare electrodes and these electrodes were characterized using a number of experimental techniques. Based on the experimental results, the electrodes showed a strong affinity towards the nitrates than phosphates. This was evident from the kinetic constants and significantly higher capacity of electrosorption. At 1mM solutions, representative of a typical wastewater, nitrate exhibited about 3.5 times higher concentration than phosphates on a molar basis. The electrodes were reasonably stable under low concentrations of nitrates. At higher concentrations, the electrodes were not completely regenerable when the desorption step was carried out at 0V. These results are covered in this manuscript.publishedVersio

P284 Evaluation of a self-management smartphone app for those living with Sjögren’s syndrome: a fully remote randomised pilot and feasibility trial

Background/Aims People with Sjögren's Syndrome (SS) experience a range of symptoms, including dryness, pain, fatigue, and poor sleep. Pharmacological management is limited, and SS patients may not have timely access to non-pharmacological support with these symptoms. Accessible evidence-based support via an app may benefit some. An evidence-based app (Sjogo) was co-developed with SS patients through a series of focus groups and workshops (n = 7). Alongside the workshops, behaviour change techniques and evidence-based intervention components were identified from the literature and known evidence-based interventions and were discussed with participants in focus groups. An app was developed containing active ingredients (e.g. features supporting behaviour change, validation of experiences, reflective activity diary, goal setting, cognitive behaviour therapy for sleep) to facilitate participation in daily activities and support symptom management. An additional control app was developed which contained “information only” content. We conducted a fully remote pilot feasibility RCT of the app. The aim of the study was to test trial procedures including recruitment rates, outcome completion, and engagement with the app. Methods The Sjogo app was released internationally for 8 weeks on Android and iOS app stores in January 2021. Potential participants were alerted to the trial through social media and patient groups. Those who downloaded the app were guided through in-app study procedures (screening, informed consent, demographic questions and baseline symptom, patient activation and quality of life outcome completion). Outcome measures included ESSPRI, Modified Fatigue Impact Scale, depression (VAS), anxiety (VAS), Sleep Condition Index, PAM-10 and ICECAP-A. Participants were randomised to an information-version (control) or full-version of Sjogo containing features supporting behaviour change. Users could engage with Sjogo as they wished and were asked to complete outcomes at baseline, 5 and 10 weeks. Results 996 participants from 33 countries downloaded Sjogo, with 617 (61.95%) completing the onboarding procedures and consenting to participate in the study. These participants were randomised to the full-version of the app (n = 318) or control-version (n = 299). Participants were mostly female (95.62%) iOS users (55.11%) from the UK (54.62%) or USA (28.92%) with a mean age of 50.97 (SD 13.75). Outcome completion rates at 5 and 10 weeks were 29.24% and 13.52% respectively for the full-version and 44.48% and 28.42% for the control-version. Conclusion Completion rates demonstrate that Sjogo can be evaluated in a real-world context in a fully powered RCT with large numbers of participants over a short timescale. However, maintaining engagement rates is challenging. App design could be optimised to maintain effective engagement with the app and support behaviour change. A process evaluation which includes further analysis of app engagement data and interviews with participants will further inform improvements to app content, features and trial procedures

Tin and Tin Alloys for Low Cost Bipolar Plates in PEM Fuel Cells

Proton Exchange Membrane (PEM) Fuel Cells are one of the most promising futures for green energy, as they provide a sustainable alternative to combustion engines in vehicles. The bipolar plate (BPP) is a crucial component in the PEM fuel cell, providing mechanical support to the stack as well as ensuring the even flow of reactants into the cell and waste products out of the cell. Additionally, it is an important conductive medium for the transfer of electrons through the stack, and any losses occurring in the BPP will reduce the overall performance of the fuel cell. Metallic materials for bipolar plates are nowadays favoured for their high conductivity and mechanical strength. However, given the harsh conditions inside a PEMFC, they will form a protective oxide on the surface, which reduces the cell performance over time due to an increase in interfacial contact resistance (ICR). Dissolution of the metal bipolar plate could also result in leaching of harmful metal ions which cause irreversible damage to the membrane. Therefore, metallic BPPs must be coated with a conductive and stable material to increase the lifetime and performance of the fuel cell. This thesis explores a new concept of soldering the gas diffusion layer (GDL) to the BPP using metallic tin (Sn). A thin layer of Sn is formed on a stainless steel BPP using electrodeposition, and then hot pressed with the GDL at a temperature close to the melting point of Sn. This leads to excellent conduction pathways through the BPP to the GDL, drastically reducing contact resistance and improving fuel cell performance. Additionally, the Sn coating will oxidise under the conditions present inside a fuel cell, leading to a protective SnO2 oxide layer which should prevent further corrosion whilst maintaining conductivity through the soldered GDL fibres. This soldering process produces a BPP/GDL system with an excellent performance and longevity inside a fuel cell, using a simple forming method and low-cost materials. BPPs produced in this way were optimised to give the lowest contact resistance and best corrosion resistance, as judged from electrochemical testing in a simulated PEMFC environment. The optimised Sn/GDL BPP was found to perform much better than stainless steel (SS316) alone, with an ICR of 6.5 mΩ cm2 and 13.2 mΩ cm2 obtained before and after corrosion testing, respectively. The increase in ICR after electrochemical testing was attributed to the dissolution and precipitation of the Sn to form a SnO2 layer, which was not completely protective. Additional modifications to the Sn/GDL system can be made to improve the stability of the protective oxide layer, and the interface between the Sn and the GDL. Both the addition of bismuth and indium as alloying elements were investigated, with additions of up to 4 % bismuth improving performance. Additions of more than 4 %, and excessive heat treatment of the samples during hot-pressing led to the phase separation of the alloy which had a detrimental effect on performance. The presence of a carbon nanolayer at the Sn/GDL interface also enhanced the conductivity of the system and specifically multiwalled carbon nanotubes maintained a high conductivity even after exposure to a simulated PEMFC environment. Three of the different Sn/GDL concept bipolar plates were tested inside a working fuel cell to compare to standard stainless steel and gold coated stainless steel bipolar plates. All three Sn/GDL, SnBi/GDL, and Sn/C/GDL BPPs performed better than stainless steel alone, with a higher cell voltage and lower ICR at all points during the 200 hours (600 drive cycles) of testing. The Sn/GDL performed the best of the three overall, with a lower degradation rate and small increase in ICR after testing. Although the SnBi and Sn/C BPPs performed well over the first 500 cycles, the harsh conditions experienced during the shut down and start-up procedures led to enhanced degradation during the final 100 cycles. It was predicted that the performance of the Sn/GDL BPP would meet and even surpass the performance of the Au coated BPP if cycling were to continue. Finally, the suitability of the Sn/GDL system on an industrial scale was analysed. Sn/GDL as a BPP material was found to be a much cheaper alternative to Au coated BPPs, with an estimated cost of 7 $ / kW compared to over 100 for gold. This is still more expensive than the industrially produced Bpps, which cost around 5 / kW, but with small improvements in performance and large scale production, the Sn/GDL BPP could be a cheaper alternative. Additionally, a unique high-throughput joining method to form fuel cell stacks by using the Sn as a solder material is proposed. This would provide a highly efficient manufacturing method and inevitably lead to further cost reductions. Therefore, the novel Sn/GDL concept for BPPs is both high performance and low cost, and represents a promising alternative to traditional coated bipolar plates for use in PEM Fuel Cells

Soldering a gas diffusion layer to a stainless steel bipolar plate using metallic tin

A novel investigation to decrease the interfacial contact resistance of stainless steel bipolar plates was performed. A thin layer of Sn was electrodeposited onto a bipolar plate and subsequently joined with a gas diffusion layer through hot-pressing at a temperature around the melting point of tin. This procedure was optimised, depositing 30 μm of Sn onto the stainless steel bipolar plate before hot-pressing at 230 °C and 0.5 bar for 20 min. A contact resistance of 5.45 mΩ cm2 at 140 N cm−2 was obtained, with low values maintained after exposure to both in-situ and ex-situ conditions. The in-situ testing in a fuel cell produced excellent results, with minor increases in contact resistance from 8.8 to 9.2 mΩ cm2 and decreases in cell voltage from 0.714 to 0.667 V after 200 h of operation. These values are comparable to gold plated stainless steel, showing that combining a gas diffusion layer with electrodeposited Sn through hot-pressing is a promising low-cost coating for bipolar plates in PEM fuel cells.acceptedVersio

Soldering a gas diffusion layer to a stainless steel bipolar plate using metallic tin

A novel investigation to decrease the interfacial contact resistance of stainless steel bipolar plates was performed. A thin layer of Sn was electrodeposited onto a bipolar plate and subsequently joined with a gas diffusion layer through hot-pressing at a temperature around the melting point of tin. This procedure was optimised, depositing 30 μm of Sn onto the stainless steel bipolar plate before hot-pressing at 230 °C and 0.5 bar for 20 min. A contact resistance of 5.45 mΩ cm2 at 140 N cm−2 was obtained, with low values maintained after exposure to both in-situ and ex-situ conditions. The in-situ testing in a fuel cell produced excellent results, with minor increases in contact resistance from 8.8 to 9.2 mΩ cm2 and decreases in cell voltage from 0.714 to 0.667 V after 200 h of operation. These values are comparable to gold plated stainless steel, showing that combining a gas diffusion layer with electrodeposited Sn through hot-pressing is a promising low-cost coating for bipolar plates in PEM fuel cells

In-Situ Monitoring of Interfacial Contact Resistance in PEM Fuel Cells

A new in situ method for measuring the interfacial contact resistance between the bipolar plate and gas diffusion layer of an operating PEM Fuel Cell has been developed. This method involves the insertion of probe wires, supported by a printed circuit board, between the catalyst-coated membrane and cathode side gas diffusion layer. Initial results suggest that the probe has no significant impact on fuel cell performance and produces real-time contact resistance measurements that are sensitive to changes in relative humidity and cell temperature, thus allowing the investigation of phenomena such as the oxidation of bipolar plate coatings during real operation