High performance platinum group metal-free cathode catalysts for microbial fuel cell (MFC)

© The Author(s) 2016. The oxygen reduction reaction (ORR) at the cathode is usually the limiting step in microbial fuel cells and improvements have to be done to increase the performances and reduce the cost. For the first time, iron-based catalysts were synthesized utilizing the polymerization-pyrolysis method and tested successfully in neutral media and in working microbial fuel cells (MFCs). The catalysts were synthesized using polymerization, salt formation, mixed with iron salt and pyrolyzed at 850°C (PABA-850) and 950°C (PABA- 950) respectively. To study the kinetics, electro-activity of the catalysts was investigated using rotating ring disk electrode (RRDE). Results showed that PABA-850 had higher catalytic activity compared to that of PABA-950. Both Fe-catalysts had much better activity compared to activated carbon (AC) used as a baseline. Catalysts were then integrated into air breathing cathodes (loading 1 mg cm-2) and tested in single chamber MFC. The power peak obtained was 178 ± 3 μWcm-2 for PABA-850. Comparable power was produced from PABA-950 (173 ± 3 μWcm-2). AC power output was 131 ± 4 μWcm-2 that was roughly 40% lower compared to Fe-based catalysts. Those results demonstrated that the addition of platinum group metal free (PGM-free) catalysts increased the output of the MFCs substantially. Fe-based catalysts seem to be suitable for large-scale MFC applications

A family of Fe-N-C oxygen reduction electrocatalysts for microbial fuel cell (MFC) application: Relationships between surface chemistry and performances

© 2016 The Author(s) Different iron-based cathode catalysts have been studied for oxygen reduction reaction (ORR) in neutral media and then applied into microbial fuel cells (MFC). The catalysts have been synthesized using sacrificial support method (SSM) using eight different organic precursors named Niclosamide, Ricobendazole, Guanosine, Succinylsulfathiazole, Sulfacetamide, Quinine, Sulfadiazine and Pyrazinamide. Linear Sweep Voltammetry (LSV) curves were obtained for the catalysts using a O2 saturated in 0.1M potassium phosphate buffer and 0.1M KCl solution and a Rotating Ring Disk Electrode (RRDE) setup in order to study the ORR characteristics. Additionally, we analyze the peroxide yield obtained for each catalyst which helps us determine the reaction kinetics. Those catalysts have been mixed with activated carbon (AC), carbon black (CB) and PTFE and pressed on a metallic mesh forming a pellet-like gas diffusion electrode (GDE). Results showed that Fe-Ricobendazole, Fe-Niclosamide and Fe-Pyrazinamide had the highest cathode polarization curves and highest power densities output that was above 200μWcm−2. Fe-Ricobendazole, Fe-Niclosamide, Fe-Pyrazinamide, Fe-Guanosine Fe-Succinylsulfathiazole and Fe-Sulfacetamide outperformed compared to Pt cathode. Fe-Sulfadiazene and Fe-Quinine performed better than AC used as control but less than Pt. Correlation of surface composition with performance showed that power density achieved is directly related to the total amount of nitrogen, and in particularly, N coordinated to metal and pyridinic and pyrrolic types while larger amounts of graphitic nitrogen result in worse performance

Influence of platinum group metal-free catalyst synthesis on microbial fuel cell performance

© 2017 The Authors Platinum group metal-free (PGM-free) ORR catalysts from the Fe-N-C family were synthesized using sacrificial support method (SSM) technique. Six experimental steps were used during the synthesis: 1) mixing the precursor, the metal salt, and the silica template; 2) first pyrolysis in hydrogen rich atmosphere; 3) ball milling; 4) etching the silica template using harsh acids environment; 5) the second pyrolysis in ammonia rich atmosphere; 6) final ball milling. Three independent batches were fabricated following the same procedure. The effect of each synthetic parameters on the surface chemistry and the electrocatalytic performance in neutral media was studied. Rotating ring disk electrode (RRDE) experiment showed an increase in half wave potential and limiting current after the pyrolysis steps. The additional improvement was observed after etching and performing the second pyrolysis. A similar trend was seen in microbial fuel cells (MFCs), in which the power output increased from 167 ± 2 μW cm−2 to 214 ± 5 μW cm−2. X-ray Photoelectron Spectroscopy (XPS) was used to evaluate surface chemistry of catalysts obtained after each synthetic step. The changes in chemical composition were directly correlated with the improvements in performance. We report outstanding reproducibility in both composition and performance among the three different batches

Effects of antiplatelet therapy after stroke due to intracerebral haemorrhage (RESTART): a randomised, open-label trial

BACKGROUND: Antiplatelet therapy reduces the risk of major vascular events for people with occlusive vascular disease, although it might increase the risk of intracranial haemorrhage. Patients surviving the commonest subtype of intracranial haemorrhage, intracerebral haemorrhage, are at risk of both haemorrhagic and occlusive vascular events, but whether antiplatelet therapy can be used safely is unclear. We aimed to estimate the relative and absolute effects of antiplatelet therapy on recurrent intracerebral haemorrhage and whether this risk might exceed any reduction of occlusive vascular events. METHODS: The REstart or STop Antithrombotics Randomised Trial (RESTART) was a prospective, randomised, open-label, blinded endpoint, parallel-group trial at 122 hospitals in the UK. We recruited adults (≥18 years) who were taking antithrombotic (antiplatelet or anticoagulant) therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage, discontinued antithrombotic therapy, and survived for 24 h. Computerised randomisation incorporating minimisation allocated participants (1:1) to start or avoid antiplatelet therapy. We followed participants for the primary outcome (recurrent symptomatic intracerebral haemorrhage) for up to 5 years. We analysed data from all randomised participants using Cox proportional hazards regression, adjusted for minimisation covariates. This trial is registered with ISRCTN (number ISRCTN71907627). FINDINGS: Between May 22, 2013, and May 31, 2018, 537 participants were recruited a median of 76 days (IQR 29-146) after intracerebral haemorrhage onset: 268 were assigned to start and 269 (one withdrew) to avoid antiplatelet therapy. Participants were followed for a median of 2·0 years (IQR [1·0- 3·0]; completeness 99·3%). 12 (4%) of 268 participants allocated to antiplatelet therapy had recurrence of intracerebral haemorrhage compared with 23 (9%) of 268 participants allocated to avoid antiplatelet therapy (adjusted hazard ratio 0·51 [95% CI 0·25-1·03]; p=0·060). 18 (7%) participants allocated to antiplatelet therapy experienced major haemorrhagic events compared with 25 (9%) participants allocated to avoid antiplatelet therapy (0·71 [0·39-1·30]; p=0·27), and 39 [15%] participants allocated to antiplatelet therapy had major occlusive vascular events compared with 38 [14%] allocated to avoid antiplatelet therapy (1·02 [0·65-1·60]; p=0·92). INTERPRETATION: These results exclude all but a very modest increase in the risk of recurrent intracerebral haemorrhage with antiplatelet therapy for patients on antithrombotic therapy for the prevention of occlusive vascular disease when they developed intracerebral haemorrhage. The risk of recurrent intracerebral haemorrhage is probably too small to exceed the established benefits of antiplatelet therapy for secondary prevention. FUNDING: British Heart Foundation

Dentigerous cyst enucleation: A conervative approach

Dentigerous cyst is a type of odontogenic cysts and generally occurs in the ages of twenties or thirties. Dentigerous cyst always includes a tooth which cannot complete the eruption process and occurs around the crown by the fluid accumulation between the layers of enamel organ. In rare cases, dentigerous cyst occurs in the first decade of life and develops in an immature permanent tooth as a result of a chronic inflammation of overlying nonvital primary tooth. In this report, a case of dentigerous cyst in primary dentition in a 9-year-old child patient and its treatment were presented. The standardized treatment for a dentigerous cyst is enucleation and extraction of the involved tooth. In cases of larger cysts, an initial marsupialization to diminish the size of the osseous defect, followed by enucleation and tooth extraction, has been advocated. However, if the patient is a child and the cyst is small, removal of cystic lining followed by extraction of deciduous tooth usually results in disappearance of the cyst and preservation of the permanent tooth. When dealing with larger lesions, enucleation and tooth extraction have been favored. This can lead to functional, cosmetic, and psychologic consequences for the child

Comparison of clinical performance of newer chemo-mechanical caries removal system and conventional cavity preparation technique in children

Objective: The study was aimed to compare the clinical performance of newer chemo-mechanical caries removal system and conventional cavity preparation technique in children. Study Design: Forty primary molars or first permanent molars of twenty children between the age groups of seven to ten years were selected randomly and divided into two groups of twenty teeth each: Group I was treated by the mechanical method and Group II with Brix 3000 gel method. The efficacy, time taken, and the pain threshold were evaluated during the caries removal by Ericson D et al. scale, stopwatch and modified visual analog scale, respectively. The preferred choice of treatment was assessed using a questionnaire. Results: The comparison between the time taken by the two methods showed a significant difference (P < 0.05). The caries removal efficacy indicated a significant difference as well ( P < 0.05). The pain rating results indicated a notable difference in the mean Visual Analogue Scale score (P = 0.001). The comparison between the two choices of treatment indicated a significant difference at p≤0.05. Conclusion: It was concluded that airotor was efficient in caries removal and while Brix 300 had lower pain rating and better patient acceptance

Fully Synthetic Approach toward Transition Metal–Nitrogen–Carbon Oxygen Reduction Electrocatalysts

We report a nonpyrolytic chemical synthesis of model iron–nitrogen–carbon electrocatalysts for oxygen reduction reaction (ORR) to elucidate the role of Fe–N centers in the catalysis mechanism. The graphene-supported and unsupported catalysts were analyzed in detail by X-ray spectroscopy techniques. The electrochemical analysis was performed by linear sweep voltammetry and square wave voltammetry in 0.5 M H₂SO₄ and 0.1 M KOH electrolytes. In this article, with the use of model catalysts, we manifest and confirm the difference in the specific role of Fe–N active sites toward ORR in acidic and alkaline environments