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 O-2 saturated in 0.1 M potassium phosphate buffer and 0.1 M 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 200 mu Wcm(-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. (C) 2017 The Authors. Published by Elsevier B.V.

A series of copper-based electrocatalysts were prepared by the Sacrificial Support Method (SSM) with variation of synthesis parameters. Thin films of the materials were evaluated for their electrocatalytic activities towards CO2 electroreduction to short-chain (C1-C2) hydrocarbons by standard electrochemical methods. Gas-phase reaction products were quantified using an online gas chromatography system. At −0.98V vs reversible hydrogen electrode (RHE), copper oxide-derived catalysts were found to have selectivity toward C2H4 approximately one order of magnitude higher than to CH4. The highest selectivity towards C2H4 production at −0.98V was demonstrated by the catalyst with cube morphology, synthesized with 20wt% Cu: 80wt% SiO2 ratio in the precursor. Possible causes for this shift in selectivity are discussed in terms of the morphology and surface/core composition as determined by scanning electron microscopy (SEM), X-Ray diffraction (XRD), and X-Ray photoelectron spectroscopy (XPS).

Development of platinum group metal free catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) requires understanding of the interactions between surface chemistry and performance, both of which are strongly dependent on synthesis conditions. To elucidate these complex relationships, a set of Fe-N-C catalysts derived from the same set of precursor materials is fabricated by varying several key synthetic parameters under controlled conditions. The results of physicochemical characterization are presented and compared with the results of rotating disk electrode (RDE) analysis and fuel cell testing. We find that electrochemical performance is strongly correlated with three key properties related to catalyst composition: concentrations of 1) atomically dispersed Fe species, 2) species in which N is bound to Fe, and 3) surface oxides. Not only are these factors related to performance, these types of chemical species are shown to correlate with each other. This study provides evidence supporting the role of iron coordinated with nitrogen as an active species for the ORR, and offers synthetic pathways to increase the density of atomically dispersed iron species and surface oxides for optimum performance.

Among the different Fuel Cell technologies, one is based on the implementation of Polymer Electrolyte Membrane fuel cells (PEMFC). Significant research effort has been directed towards replacement of the platinum by materials mainly consisting of metal–nitrogen–carbon (MNC) network. The knowledge derived from tens of years of optimization of Pt-based PEMFC can not be directly translated to MNC catalytic systems due to different approaches in making catalyst layers. The structure of the active site/sites of the PGM-free ORR electrocatalysts remains contentious even after 50 years of research. The structure of the active site within the Membrane Electrode Assembly (MEA) has not been studied at all. It is necessary to understand the effect of the interaction of ionomer and catalyst on the structure of the active site, morphology of catalyst layer and durability. There is a missing link between durability and activity parameters as well as chemical and morphological changes that occur inside the catalyst layer during the oxygen reduction reaction in a fuel cell. In this study, we are investigating a series of MNC electrocatalysts synthesized by the same sacrificial support route[1] and their performance in MEA. Chemistry of the electrocatalysts and catalyst layers is studied by XPS. The types of nitrogen and iron-nitrogen functionalities that are present in these materials are in-plane defects such as graphitic N and N-coordinated to three or four nitrogens and a multitude of possible edge sites such as pyridinic, pyrrolic, quaternary and Fe-N2/Fe-N sites. [2, 3] In the catalyst layers, the makeup of the active site may be affected by the interactions with negatively charged sulfonate group of nafion. Due to this interaction between groups on the catalyst surface and sulfonate groups of nafion, the rearrangement in high binding energy range has been observed. The higher relative amount of peaks between 401-403 eV in the catalyst layers is due to the shift in the position of other peaks due to interaction with an ionomer. DFT calculations were used to evaluate the strength of the interaction between different types of nitrogen containing defects and sulfonate groups and to calculate binding energy shifts of N 1s spectra upon ionomer binding. [4] Figure 1 shows DFT calculated adsorption energies of sulfonate groups on nitrogen defects. High adsorption energies particularly for protonated nitrogens which may be either pyrrolic or protonated pyridine nitrogen is observed. Moreover, the higher amount of protonated nitrogens in catalyst layer results in worse MEA performance. The pore structure is critical to the transport of oxygen to active sites and removal of water. The change in pore structure induced by the chemical changes introduced during fuel cell operation has to be understood in order to design PGM-free electrocatalyst with highest possible lifetime. The morphology of catalyst layers will be analyzed by focused ion beam/scanning electron microscopy (FIB-SEM) sectioning. This will allow to obtain a 3D visual representation of morphology of catalysts layers and to estimate in detail the evolution of structural parameters such as: specific surface area, total porosity, connectivity of pores and others as a result of degradation studies. 1. Serov, A., et al., Nano-structured non-platinum catalysts for automotive fuel cell application. Nano Energy, 2015. 16: p. 293-300. 2. Jia, Q., et al., Spectroscopic Insights into the Nature of Active Sites in Iron-Nitrogen-Carbon Electrocatalysts for Oxygen Reduction in Acid and the Redox Mechanisms. Nano Energy, 2016. 3. Artyushkova, K., et al., Chemistry of Multitudinous Active Sites for Oxygen Reduction Reaction in Transition Metal-Nitrogen-Carbon Electrocatalysts. Journal of Physical Chemistry C, 2015. 119(46): p. 25917-25928. 4. Kabir, S., et al., Binding energy shifts for nitrogen-containing graphene-based electrocatalysts – experiments and DFT calculations. Surface and Interface Analysis, 2016. Figure 1

Bioelectrochemical systems (BESs) are novel systems that utilize biological reactions coupled with electrochemical reactions for organics removal [1], electricity production [1,2] or product/nutrients recovery [2]. Specific attention was dedicated to the electrodes materials improvements. The anode material selected is usually based on three-dimensional conductive carbonaceous materials in order to respond to the necessary features that the anode needs for the optimum oxidation reaction. Particularly, the anode has to be: i) electrically conductive, ii) biologically friendly to accommodate bacteria, iii) mechanically durable and corrosion-free, iv) low cost. The main problem is instead related with the cathode. In fact, at neutral working pH, the cathode suffers of tremendous losses mainly due to activation overpotentials and low kinetics. Enzymatic based cathode have been showed to have the lowest overpotentials [3] but it has also been showed the enzyme are not very durable under “clean” or “polluted” conditions. Metal-free catalysts based on carbonaceous materials have been also used for the oxygen reduction reaction (ORR) in neutral media. Those carbonaceous materials possess high surface area, electronic conductivity, mechanical strength and durability over time and consequently can be considered suitable for microbial fuel cell (MFC) application. We have showed previously that the addition of an iron-based catalyst in an air-breathing gas diffusional electrode increased significantly the performance compare to activated carbon (AC) cathode [4]. In that study, iron-aminoantipyrine (Fe-AAPyr) was used as cathode catalyst and the catalyst was prepared using sacrificial support method with FeNO3 as a metal source and aminoantipyrine as a nitrogen-rich precursor. The advantage of Fe-AAPyr compared to AC cathode was 50% [4]. We have also successfully tried Fe-AAPyr in double chamber MFC [5] and in ceramic-based MFC [6]. In this work, eight novel catalysts have been synthesized, characterized chemically and morphologically and the electrochemical performances have been studied in clean condition and in a working MFC. The novelty of the catalysts was in the low-cost organic precursors utilized during the preparation. The organic precursors used were named: niclosamide, ricobendazole, guanosine, succinylsulfathiazole, sulfacetamide, quinine, sulfadiazine and pyrazinamide. SEM images showed clear 3-D structure typical from the sacrificial support method utilized. XPS showed 2- 3% of atomic nitrogen with the distribution of different types of nitrogen species typical for M-N-C obtained by SSM. Pyridinic nitrogen and nitrogen coordinated to the metal, which have been shown to be important species for ORR [7] are detected in significant amounts. The catalysts have been embedded into a mixture of AC, carbon black (CB) and PTFE and pressed on a stainless steel mesh. The cathode configuration was an air breathing gas diffusion electrode. The new catalysts have been compared with Pt and AC used as a control. The cathode was inserted on a lateral hole of a single chamber MFC. Cathode polarization curves were run in phosphate buffer. Results showed that six catalysts (Fe-Ricobenzadole, Fe-Niclosamide, Fe-Pyrazinamide, Fe-Guanosine Fe-Succinylsulfathiazole and Fe-Sulfacetamide) outperformed compared to Pt and all outperformed compared to AC. Similar trend was achieved when the cathodes were inserted in working MFCs (Figure 1). Actually three catalysts (Fe-Ricobenzadole, Fe-Niclosamide and Fe-Pyrazinamide) had the highest power density output that was measured between 202 and 209 μWcm-2 (Figure 1). Correlations between surface properties and performance showed a linear relationship between the power achieved and the amount of pyridinic nitrogen, nitrogen coordinated to metal and pyrrolic nitrogen. The positive role of Nx-Fe and pyridinic nitrogen for ORR in acidic and alkaline conditions has been shown before [7]. In contrast to the observations in this report, in an acidic environment, pyrrolic N causes partial reduction of oxygen to hydrogen peroxide thereby reducing an overall activity. References [1] X. Wang, C. Santoro, P. Cristiani, G. Squadrito, Y. Lei, A. G. Agrios, U. Pasaogullari, B. Li. J. Electrochem. Soc. 160 (7), G117 (2013). [2] I. Gajda, J. Greenman, C. Melhuish, C. Santoro, B. Li, P. Cristiani, I. Ieropoulos. Sustainable Energies Technologies and Assessments 7, 187 (2014). [3] C. Santoro, F. Soavi, A. Serov, C. Arbizzani, P. Atanassov. Biosens. Bioelectron. 78, 229 (2016). [4] C. Santoro, A. Serov, C.W. Narvaez Villarrubia, S. Stariha, S. Babanova, K. Artyushkova, A.J. Schuler, P. Atanassov. Sci. Rep. 5, 16596 (2015). [5] C. Santoro, A. Serov, C.W. Narvaez Villarrubia, S. Stariha, S. Babanova, A.J. Schuler, K. Artyushkova, P. Atanassov. ChemSusChem 8(5), 828 (2015). [6] C. Santoro, K. Artyushkova, I. Gajda, S. Babanova, A. Serov, P. Atanassov, J. Greenman, I. Ieropoulos, A. Colombo, S. Trasatti, P. Cristiani. Int. J. Hydrogen Energy 40(42), 14706 (2015) [7]. K. Artyushkova, A. Serov, S. Rojas-Carbonell, P. Atanassov, J. Phys. Chem. C 119 (46), 25917 (2015). Figure 1

Research into alternative catalysts for the oxygen reduction reaction in PEMFCs continues to advance due to ongoing efforts to understand structure-to-property relationships in these materials. Though much work has been done on platinum group metal free (PGM-free) catalysts for the ORR, there is still a need to develop tangible relationships between synthesis methods, morphology, chemistry, and performance of these materials. One catalyst that has shown promise for both performance and durability is synthesized from precursors of iron salts and nicarbazin (Fe-NCB) using the sacrificial support method (SSM).1 Though synthesis procedures for this catalyst have been well optimized, there has not been a systematic study of structure-to-property relationships and how they relate to synthesis parameters. In addition to fundamental properties of the catalyst itself, knowledge of how the material integrates into the electrode in an operational fuel cell is critical. To address this issue, both electrochemical testing and data from an operational fuel cell are required. Further, to be able to understand interactions between individual catalyst particles, and their interactions with ionomer in the catalyst layer, analysis of the catalyst must include measurement of chemistry and morphology both for the bulk and the surface. To elucidate relationships between morphology, chemistry, and performance, a multivariate study on synthesis parameters and outcomes will be presented. TEM-EDS maps will be acquired and analyzed to examine nanoscale elemental distributions. Concentrations of atomically dispersed Fe with respect to particle and carbon plane edges, as well as the presence of Fe nanoparticles will be addressed. Correlations between location specific relative concentrations of Fe and N will be explored for correlations with performance, morphology, peroxide generation, and potentials for the Fe+2-Fe+3 transition. To address bulk carbon crystallite structure including stacking order, layer strain, and lateral crystallite size, a curve fitting algorithm will be applied to XRD spectra of these materials.2 Graphitic content and strain analyses will be related to both TEM observations and XPS chemical analysis. Morphology characterization will be completed by pore size analysis with nitrogen isotherms, catalyst surface analysis using the discrete wavelet transform, and particle size distributions. Relationships between catalyst structure from sub-nanometer to micron scale, elemental distributions within individual catalyst particles, electrochemical performance, and fuel cell performance will be elucidated and presented. 1. Serov, A.; Artyushkova, K.; Niangar, E.; Wang, C.; Dale, N.; Jaouen, F.; Sougrati, M.-T.; Jia, Q.; Mukerjee, S.; Atanassov, P. Nano-structured non-platinum catalysts for automotive fuel cell application. Nano Energy 2015, 16, 293-300. 2. Shi, H.; Reimers, J.; Dahn, J. Structure-refinement program for disordered carbons. Journal of applied crystallography 1993, 26, 827-836. Figure 1

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 0.1 M potassium phosphate buffer and 0.1 M 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 200 Wcm−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. © 2016 The Author(s). Published by Elsevier B.V. This is an open access article under the CC

Direct methanol fuel cells (DMFCs) offer great advantages for the supply of power with high efficiency and large energy density. The search for a cost-effective, active, stable and methanol-tolerant catalyst for the oxygen reduction reaction (ORR) is still a great challenge. In this work, platinum group metal-free (PGM-free) catalysts based on Fe-N-C are investigated in acidic medium. Post-treatment of the catalyst improves the ORR activity compared with previously published PGM-free formulations and shows an excellent tolerance to the presence of methanol. The feasibility for application in DMFC under a wide range of operating conditions is demonstrated, with a maximum power density of approximately 50 mW cm(-2) and a negligible methanol crossover effect on the performance. A review of the most recent PGM-free cathode formulations for DMFC indicates that this formulation leads to the highest performance at a low membrane-electrode assembly (MEA) cost. Moreover, a 100 h durability test in DMFC shows suitable applicability, with a similar performance-time behavior compared to common MEAs based on Pt cathodes.

Fe-based catalysts based on ricobendazole and niclosamide showed higher performance compared to Pt (20–25%) and AC (90–99%) and more durability in long terms operations.

It is well known that CO2 is a major green-house gas with significant influence on increase of overall global temperature. Recent work on CO2, however, has shown that it can be used as feedstock for production of value-added products such as alcohols, formate, CO, and methane or ethane [1]. Electrochemical conversion is one way of utilizing CO2 with the advantage of easier scale-up and operation under ambient temperature and pressure. This technology is currently in the developmental stage and can therefore benefit from the knowledge obtained from research in the field of the proton exchange membrane fuel cell (PEMFC) or even anion exchange membrane fuel cells (AEMFCs). Similar to the oxygen reduction reaction (ORR) in PEMFCs/AEMFCs, the reaction at the cathode of a CO2 electrolyzer requires an engineered electrocatalyst. Furthermore, it should be mentioned that contrary to the ORR, CO2 electroreduction reaction results in multiple reaction products that are generated both in liquid and gas phase and the hydrogen evolution reaction (HER) is a competing reaction. In order to make the CO2 electroreduction systems viable and prevent cost-heavy separation of products, electrocatalysts with high selectivity towards the desired product should be designed, synthesized, and scaled-up. Herein we report our recent results on synthetic development method – based on Sacrificial Support Method (SSM) for preparation of mono- and bi-metallic materials [2-5]. The method of the evaluation of electrocatalytic activity of un-supported catalysts for the CO2 electroreduction reaction was based on the rotating disk electrode (RDE) technique and online gas chromatography (GC). The sealed RDE cell was specially designed at Naval Research Laboratory and it was demonstrated that the reaction products generated on small surface area thin RDE films can be quantified by online GC. Liquid reaction products are separated and identified ex-situ by liquid chromatography or NMR (experiments performed at UNM). Figure 1 shows SEM morphology of copper-based electrocatalysts, XRD data and electrochemical performance from RDE experiments. It was shown that, by controlling the SSM parameters, it was possible to synthesize electrocatalysts selective to one product only (except hydrogen). Acknowledgements OAB is grateful to the Office of Naval Research for financial support of this project. References [1] Y. Hori, Electrochemical CO2 reduction on metal electrodes, in: C.e.a. Vayenas (Ed.) Modern Aspects of Electrochemistry, vol. 42, Springer, New York, 2008. [2] A. Serov, K. Artyushkova, N. I. Andersen, S. Stariha, P. Atanassov "Original Mechanochemical Synthesis of Non-Platinum Group Metals Oxygen Reduction Reaction Catalysts Assisted by Sacrificial Support Method", Electrochim. Acta (2015) doi:10.1016/j.electacta.2015.02.108 [3] A. Serov, N. I. Andersen, A. J. Roy, I. Matanovic, K. Artyushkova, P. Atanassov, “CuCo2O4 ORR/OER Bi-Functional Catalyst: Influence of Synthetic Approach on Performance”, J. of The Electrochem. Soc., 162 (4) (2015) F449-F454 [4] C. Santoro, A. Serov, C. W. Narvaez Villarrubia, S. Stariha, S. Babanova, A. J. Schuler, K. Artyushkova, P. Atanassov. “Double‐Chamber Microbial Fuel Cell with a Non‐Platinum‐Group Metal Fe–N–C Cathode Catalyst”, ChemSusChem, 8 (2015), 828-834. [5] N. I. Andersen, A. Serov, P. Atanassov “Metal Oxides/CNT Nano-Composite Catalysts for Oxygen Reduction/Oxygen Evolution in Alkaline Media”, Appl. Catal. B: Environmental, 163 (2015), 623-627. [6] Z. Zhang, K.L. More, K. Sun, Z. Wu, W. Li, Chemistry of Materials, 23 (2011) 1570. [7] S. Trasatti, O.A. Petrii, Pure and Applied Chemistry, 63 (1991) 711. Figure 1