Iron Phthalocyanine and MnOx composite catalysts for Microbial Fuel Cell applications Created inline with the EPSRC requirement for open access articles, containing... Introductory information - For each data filename, a short description of what data is contained - Explain the relationship between multiple data sets (if required) - The date of data collection - Key words used to describe the data topic Methodological information - A brief method description – what the data is, how and why it was collected, and how it was processed - Outline any missing data - Reference to the publication Data-specific information - Full name and definitions of column headings for tabular data - Units of measurement Introductory information The .XLSX file entitled "Data for main manuscript figures" contains 9 tabs, one for each Figure and table. The data presented in the Figures is encompassed by the blue box. KEYWORDS Iron Phthalocyanine Microbial Fuel Cell Oxygen Reduction Reaction Manganese Dioxide Disproportionation X-Ray Photoemmision Spectroscopy (XPS) Composite Power Density ACCRONYMS AND NAMES Catalysts are refered to with the following contractions referred to in all Figures in "Data for main manuscript figures" and "Data for main supplementary figures" FePc/MON - Iron Phthalocyanine deposited on Monarch 1000 Carbon using H2SO4 deposition solvent Monarch - Unmodified Monarch Carbon FePcMnOx/MON - The catalyst "FePc/MON" is subject to an MnOx deposition step using equilibrium adsorption of Mn2+ followed by oxidation with MnO4- (Manganate) followed by washing MnOx/MON - The unmodified "Monarch" was subject to an MnOx deposition step using equilibrium adsorption of Mn2+ followed by oxidation with MnO4- (Manganate) followed by washing Pt/C - Commerical Carbon supported Platinum catalyst (Etek), at 20% Pt weight. Throughout the excel sheet the measured potentials have been corrected by measuring the refernce electrode vs a new Ag|AgCl reference electrode then 0.622V added to obtain the potential vs RHE. In all .xlsx files the data presented in the manuscript is shaded in light blue. The date at which the data was obtained is shaded in pink. The references to source data for tables are shaded in yellow. BRIEF DESCIRPTION OF DATA For the .xsls data file "Data for main manuscript figures" the following data is contained.... The results of a slow potential scan experiment of GDC half cells with air cathodes supporting a catalytic layer of a certain catalyst in O2 saturated PBS. (Tabs Fig. 1 and Table 1) The results of Microbial Fuel Cell air cathodes during steady state operation and during polarisation with resistor substituion to produce a power curve in buffered wastewater medium. (Tabs Fig. 4, Fig. 5, Table 4 and Table 5) Baseline corrected XPS results for each catalyst with model peaks for photoemissions from Manganese and Iron, and specific Nitrogen chemical groups being taken from the literature and fit to the experimentally obtained data. (Tabs Fig. 3 and Table 3) Rotating Ring Disc Electrode studies of thin films of each catalyst in medium of O2 saturated Phosphate media. The results of cathodically polarising air cathodes which bear manganese dioxide and relating the data to solvated Mn2+ detected in the electrolyte after the experiment (Tabs Fig. 2 and Table 2) For the .xsls data file "Data for main supplementary figures" the following data is contained.... Comparing the results obtained in O2 and N2 saturated electrolyte for a fast potential scan experiment on GDC half cells with air cathodes supporting a catalytic layer of a certain catalyst. (Tabs Fig. A.4) The results of non-polarisation vs cathodically polarising air cathodes which bear manganese dioxide and relating the data to solvated Mn2+ detected in the electrolyte after the experiment (Tabs Fig. A.2 and Table A-1) Evolution of the open circuit potential over a 15hrs period for GDC half cells with different air cathodes in O2 saturated PBS. (Tabs Fig. A-3) Baseline corrected XPS results for each catalyst with model peaks for photoemissions from specific Oxygen chemical groups being taken from the literature and fit to the experimentally obtained data. (Tabs Fig. A.5) UNITS AND HEADINGS For the .xsls data file "Data for main manuscript figures" the following definitions apply to each data heading Tab "Fig. 1": Air-FePc/MON - Air saturated solution in contact with air cathode supporting a catalyst layer of catalyst FePc/MON Rs=290 Ohms --- The solution resistance between working and reference electrode was measured at 290 Ohms and this was used to correct the applied potential data post measurement. Ewe --- Working Electrode Potential. Units / Volts vs the reversible hydrogen electrode I - Working electrode current. Units / Amps J - Working electrode current density. Units / Amps per cm-2 geometric area |J| - +ve values of "J". Used for compiling tafel plot. Units / Amps per cm-2 geometric area Tab "Fig. 2": E --- Working Electrode Potential. Units / Volts vs the reversible hydrogen electrode N Average - Average N value - number of electrons consumed per O2 molecule. Unitless Tab "Fig. 3": Sample # --- The same prepared catalyst sample was scanned at 1-4 points for average values to be taken, the Sample # refers to which scan on the catalyst surface that data relates to. Binding Energy (Eb) --- Factor during X-ray Photoemmision Spectroscopy. Energy of photon emitted during relaxation of photoexcited electron back to its rest state. Units / eV (electron volts) Photoemissions --- Counts per time unit of a photon detected with a specific kinetic/binding energy. Units / Counts s-1 Chemical Groups (NAMES) --- Deconvolutiong the Counts vs. Binding Energy results into photoemissions from certain chemical groups which are (named) and pictorally represented in Fig. 3. The factors of the gaussian peak are selected from the literature using the same constrained Eb and W1/2 (or peak half width. Units / eV) values when peak fitting in CasaXPS. Tab "Fig. 4": MFC # Ecathode --- The cathode potential of a specific Microbial Fuel Cell. Time (MFC #) --- The time after inserting fresh cathodes into a particular MFC for a particular cathode catalyst. Units / Hrs (after inserting certain cathode) Tab "Fig. 5": Cell Power --- The power density of a microbial fuel cell under a specific external resistance. Units / Watts metre^-2 geometric area. calculated using P=VI Current Density --- The current density of a microbial fuel cell under a specific external resistance. Units / Amps metre^-2 geometric area. E Cathode --- Cathode potential of a microbial fuel cell under a specific external resistance. Units / Volts vs reversible hydrogen electrode Cell Voltage --- Cell Voltage of a microbial fuel cell under a specific external resistance. Units / Volts Tab "Table 1": Tafel slope --- taken from 1mV/s data in Fig.1 as the slope of log10(I) vs E. Units / Volts per decade of current. This data is separated into individual electrochemical processes - "ORR wave" relates to oxygen reduction catalysed by that surface, MnOx reduction refers to the wave from electrochemical MnOx reduction, 2nd tafel region refers to the tafel wave at higher overpotential. J0 --- Exchange current taken from Fig.1 by extrapolating the tafel slope to the OCP. EOnset --- The potential during staircase voltammetry at which current changes direction. RAS --- Redox Active FePc Sites - correlated to the amount of surface chelated iron. Units / x10^15 per cm2 JWE --- Working Electrode current density at a given potential (0.522V vs RHE in this case). Units / Amps per cm2 E @ (-0.4A cm-2) --- Working electrode potential when 0.4 Amps are passed per m2. Units / Volts vs reversible hydrogen electrode OCP (16hrs) --- Stable working electrode OCP. Units / Volts vs reversible hydrogen electrode. Tab "Table 2": Electrode (Bold) / Electrode Polarisation (Italics) --- The electrode catalyst and binder are written in bold and duplicate electrodes were either polarised or left at OCP (written in italics) Mn loading / mg --- The loading of Manganese on each electrode at the start of the experiment. Units / mg of Manganese Total Manganese Content --- The recorded concentration of manangese (parts per million) in the electrolyte solution at the end of the electrochemical experiment. Units / parts per million Leached Mass of Mn from electrode --- The integration of charge passed through electrical current. Units / mg of Manganese Tab "Table 3": Oxygen (MeOx) --- % of total atomic surface species in the form of Oxygen bound as Manganese Oxide Oxygen (Other) --- % of total atomic surface species in the form of Oxygen, all forms other than oxygen bound as Manganese Oxide Tab "Table 4": Max Ecat --- The maximum open circuit cathode potential recorded in wastewater PBS with that particular catalyst. Units / Volts vs the reversible hydrogen electrode. Max Vcell --- The maximum open circuit cell potential recorded in wastewater PBS with that particular catalyst. Units / Volts. Pmax --- The maximum cell power density recorded in wastewater PBS with that particular catalyst during steady state polarisation experiments. Units / Watts per m2. Rint --- The total internal resistance of MFCs in wastewater PBS with a particular catalyst calculated from the linear voltage drop region of a polarisation experiments. Units / Ohms. Ecat @ 0.4A m-2 --- Cathode potential at a cell current density at 0.4 Amps per m2. For the .xsls data file "Data for main supplementary figures" the following definitions apply to each data heading Tab "Fig. A-2": Scan rate --- Rate at which the applied potential to the electrode surface is incrementally changed. Units / Volts s-1 Electrolyte --- Composition of the electrolyte - Nitrogen saturated Phosphate Buffer solution, pH7 in this case. #Scan --- In this experiment the results from the first three Linear Sweep Voltammogramms are presented. #Scan refers to which scan number is being represented. Unitless EWE --- Working Electrode Potential. Units / Volts vs the reversible hydrogen electrode I --- Working Electrode Current. Units / Amps. J --- Working Electrode Current Density. Units / Amps per m2 (geometric). Tab "Fig. A-3": Time - Time after immersing electrode in Phosphate Buffer Electrolyte. Units / Seconds or Hours OCP - Open Circuit Potential of air cathode with catalyst layer of a specific catalyst. Data is reported as a function of time. Units / Volts vs the reversible hydrogen electrode Tab "Fig. A-4": EWE --- Working Electrode Potential. Units / Volts vs the reversible hydrogen electrode I --- Working Electrode Current. Units / Amps. J --- Working Electrode Current Density. Units / Amps per m2 (geometric). "5mV/s N2 PBS 2nd scan" means that the cyclic voltammogramm data is collected with a voltage sweep rate of 5millivolts per second. The second scan CV data is reported as a stable response has been attained. Tab "Fig. A-5": Catalyst# --- The same prepared catalyst sample was scanned at 1-4 points for average values to be taken, the Catalyst# refers to which scan site on a specific catalyst surface the data relates to. The table in pink is pasted from CasaXPS and shows the attributes of each of the individual photoemission peak fitted to the data and the constraints in peak half width (W1/2), binding energy position and photoemission area. Binding Energy (Eb) --- Factor during X-ray Photoemmision Spectroscopy. Energy of photon emitted during relaxation of photoexcited electron back to its rest state. Units / eV (electron volts) Photoemissions --- Counts per time unit of a photon detected with a specific kinetic/binding energy. Units / Counts s-1 Chemical Groups (NAMES) --- Deconvolutiong the Counts vs. Binding Energy results into photoemissions from certain chemical groups which are (named) and pictorally represented in Fig. 3. The factors of the gaussian peak are selected from the literature using the same constrained Eb and W1/2 (or peak half width. Units / eV) values when peak fitting in CasaXPS. RSF --- Relative sensitivity Factor (a constant for each element used to modify a counts per second * binding energy value to create a value for atomic prevalence value). Unitless Area constraints --- A maximum and minimum area value for each of the specified peaks obtained during area fitting. W1/2 constraints --- The maximum and minimum peak half width values permitted for a particular peak fitted to the data. Position constraints --- The maximum and minimum binding energy at which a particular peak can occur when fitting the data. % concentration --- The atomic prevalence percentage of a particular O1s phototransmission for a particular chemical group as a percentage of the entire O1s signal. Line Shape --- Shows how gaussian/lorentzian the peak is. Measured as a percentage as GL(%). MISSING DATA Although there is no missing data for the figures in this manuscript, there are two occasions where the entire data set is not included in the Excel file.. 1) File "Data for main supplementary figures" tab "Table A-1". The OCP data here was taken as a single discrete measurement rather than a data file recorded from the Potentiostat. This table also contains a series of Manganese ppm values which were recorded by David Dunbar in the "Advanced Chemical & Materials Analysis" suite in the Bedson Building, Newcastle University 2) File "Data for main supplementary figures" tab "Fig A-5" is presented as a graph pasted from the programme CasaXPS. The original .VMS data file can be made available upon reqeust but the entire data could not be exported in the demo version. The individual O1s source emission data is presented as characteristics of the peak rather than the full data. FIGURE METHODOLOGY, EXPLANATIONS AND MOTIVATION OF STUDY For the .xsls data file "Data for main manuscript figures" the following definitions apply to each data heading Answers are organised for each Figure Fig. 1. A Gas Diffusion Electrode Half-Cell was fitted with air cathodes supporting a solution side facing catalyst layer. Electrodes were allowed to stabilise overnight then polarised. catalytic activity was measured with current. This method approximates air cathode performance in a microbial fuel cell without the added complication of biofilm varaince between studies. Fig. 2. An experiment with a rotating ring disc electrode. The disc is modified with a 71 microgramm per cm2 film of each of the catalysts. The assembly is rotated at 200rpm and the disc poised at a potential high enough to oxidised peroxide but produce little background current when peroxide is absent. The disc is then polarised with linear sweep voltammetry and the amount of H2O2 released at each potential is measured with the ring. The data is treated to obtain only the oxygen reduction current (disc) and compare it to only the peroxide oxidation current. This treatment allows mechanism data to be obtained at low overpotential. The result is expressed as the average number of electrons consumed per oxygen atom being electrochemically reduced over a potential window. The aim was to study the partial release of peroxide and how MnOx co-catalyst affects its decomposition. Fig. 3. X-ray Photoemmision spectra of catalyst powders mounted on a conductive support then bombarded with Aluminium anode monochromatic photons. The results for Nitrogen are broken into individual photoemissions for single chemical groups. The aim of this experiment was threefold; i) to verify succesful catalyst loading, ii) to find evidence of interaction between FePc and MnOx in the form of a peak shift and iii) to calculate the relative surface amount of each catalyst. Fig. 4. Microbial Fuel Cell cathode potentials when the cell is operated in phosphate buffered wastewater. The cells have different cathode catalysts and are operated over several external loads, drawing varying amounts of current. The purpose of this experiment was to validate the half-cell study and prove performance enhancement in the intended wastewater electrolyte and to show that the compsoite catalyst was relatively inert to cross over reactions. Fig. 5. Cathode potentials, cell voltages and power densities for platinum and FePcMnOx/MON composite cathodes during polarisation curves in phosphate buffered wastewater. Motivation of study as in Fig. 4. Table 1. A tabulated summary of catalyst performance indicators when an air cathode mounted in a half cell is subjected to steady state Linear sweep voltammetry. Motivation of study as in Fig. 1. Table 2. Inductively Couple Plasma analysis of electrolytes which have been in contact with MnOx/MON and FePcMnOx/MON electrodes with and without polarisation. The electrolyte samples are filtered prior to ICP analysis. The aim of the experiment was to demonstrate that the MnOx catalyst is retained in the film by comparing the charge passed with electrolyte concentrations. Table 3. Atomic Prevalence XPS analysis. The surface of each catalyst sample is reported considering Carbon, Nitrogen, Iron, Manganese, Sulphur and Oxygen (excluding detected Potassium and undetectable hydrogen). Potassium and sulphur could be included by comparing the peak in the 200eV survey scan data and comparing it to the Carbon peak. The same ratios were assumed for 50eV. The method is described in the supplementary information. Motivation of study as in Fig. 3. Table 4. Summary of microbial fuel cell performances in phosphate buffered wastewater when fitted with different air cathode catalysts. Power density obtained during polarisation curves. Motivation of study as in Fig. 4. For the .xsls data file "Data for main supplementary figures" the following definitions apply to each data heading Fig. A.2. First second and third LSV polarisations of composite air cathodes in Phosphate buffer. The result highlights the fact that a portion of the MnOx undergoes a reductive transformation. Motivation of study as in Table 2. Fig. A.3. Open circuit potential evolution of several air cathodes with different binders and connectors attached to MnOx bearing catalyst films immersed in air saturated phosphate buffer. This aim of this experiment was to show that a stable potential is obtained without polarisation and that binder and wire connector do not significantly effect the open circuit potential. Fig. A.4. Cyclic Voltammogram of electrochemically aged air cathodes of FePc/MON and FePcMnOx/MON demonstrating the Fe(II/III) redox in de-aerated solutions and how this relates to oxygen reduction in aerated solution of phsophate buffer. The aim of this experiment was to demonstrate that FePc was not decomposed by MnO4- oxidising agent in the composite and that a subsequent coating of MnOx does not greatly influence the Fe(II/III) redox potential. Fig. A.5. X-ray photoemission spectra of the O1s phototransmission relating to oxygen for all catalysts. The aim of this experiment was to determine what oxidation state the MnOx is present in. Table A.1. Results of pH and conductivity measurements of aerated phosphate buffer before and after polarisation of submerged MnOx bearing electrodes. OCP of electrodes measured prior to experiment. The aim of this experiment was to evaluate the potential reactants and products of cathodically polarising MnOx by identifying pH and conductivity changes. DATE OF DATA ACQUISITION The data for acquisition of each portion of data is written on the .xsls files highlighted in pink in column G or row 3.