Performance of a Pd-Zn Cathode Electrode in a H2 Fueled Single PEM Fuel Cell

A 21.7 wt.% Pd—7.3 wt.% Zn/C electrocatalyst prepared via the wet impregnation (w.i.) method was deposited onto commercial carbon cloth (E-TEK) and tested towards its electrocatalytic performance as a cathode electrode material for oxygen reduction reaction (ORR) in a H2 fueled single proton-exchange membrane fuel cell (PEMFC). A commercial PtRu electrode (E-TEK) was used as PEM anode for hydrogen oxidation reaction (HOR). The performance of the aforementioned PEMFC was compared with that of the same PEMFC with two different Pt-based cathodes, which were prepared by deposition onto commercial carbon cloth (E-TEK) of 29 wt.% Pt/C synthesized via w.i. and of commercial 29 wt.% Pt/C (TKK). The metal loading of the tested cathode electrodes was 0.5 mgmet cm−2. Comparison was based both on polarization curves and on electrochemical impedance spectroscopy (EIS) measurements at varying cell potential. In terms of power density, the lowest and highest performance was exhibited by the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode and the PEMFC with the commercial 29 wt.% Pt/C (TKK) cathode electrode, respectively. This behavior was in accordance with the results of EIS measurements, which showed that the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode exhibited the highest polarization resistance

Development of bimetallic electrocatalysts for low-temperature fuel cells

Bimetallic electrocatalysts were studied towards the electrochemical oxygen reduction reaction (ORR) and the electrochemical hydrogen oxidation reaction (HOR) in acidic and alkaline environment mainly applying the rotating disk electrode (RDE) technique using a thin electrocatalytic film. Carbon black (Vulcan XC72R) supported Pd based bimetallic electrocatalysts 7.5 wt.% Pd – 2.5 wt.% M prepared via the wet impregnation method and reduced at 300 oC at H2 flow were tested towards their ORR and HOR activity in 0.1M HClO4 and 0.1M KOH. The aforementioned electrocatalysts were also examined as it concerns their physicochemical characteristic applying BET, XRD, TEM, SEM and XPS. Pt-based electrocatalysts with the same metal loading were also tested as reference materials. Pd-based electrocatalysts with higher metal loading (29 wt.%) applying the optimum reduction temperature and the optimum Pd:M ratio for which the activity towards the aforementioned reaction was maximized was compared with the performance of Pt-based electrocatalysts with the same metal loading. The electrocatalysts with 29 wt.% metal loading were also tested towards their stability. In the case of ORR in acidic medium the effect of the synthesis method as well as the carrier on the activity was also tested. Moreover, the activity of carbon black supported 10 wt.% Pt-M (M:Ag, Cu, Fe, Ni, Sn, Zn) towards the ORR in acidic medium in the presence and absence of EtOH was tested. Finally, the most active towards the ORR bimetallic 22 wt.% Pd – 7 wt.% Zn/C electrocatalyst was studied as cathodic electrode in a H2-fuelled PEMFC. The performance of the latter was compared with the activity of Pt-based electrocatalysts which were also used as cathodic materials.Στην παρούσα εργασία έγινε μελέτη νέων διμεταλλικών ηλεκτροκαταλυτών για την ηλεκτροχημική αντίδραση της αναγωγής του Ο2 (Oxygen reduction reaction, ORR) και την ηλεκτροχημική αντίδραση της οξείδωσης του Η2 (Hydrogen oxidation reaction, HOR) σε όξινο και αλκαλικό περιβάλλον, η οποία πραγματοποιήθηκε κύρια με την τεχνική του ηλεκτροδίου περιστρεφόμενου δίσκου με τον ηλεκτροκαταλύτη ως εναπόθεμα μικρού πάχους (thin-film rotating electrode technique, RDE). Πιο συγκεκριμένα, μελετήθηκε η δραστικότητα ως προς ORR, τόσο σε διάλυμα 0.1M HClO4 όσο και σε διάλυμα 0.1Μ ΚΟΗ, βασισμένων σε Pd διμεταλλικών ηλεκτροκαταλυτών 7.5 wt.% Pd – 2.5 wt.% M στηριγμένων σε αγώγιμο άνθρακα (Vulcan XC72R) οι οποίοι παρασκευάστηκαν κύρια με τη μέθοδο του υγρού εμποτισμού και υπέστησαν αναγωγή υπό ροή Η2 στους 300 oC. Οι ηλεκτροκαταλύτες αυτοί μελετήθηκαν επίσης όσον αφορά στη δραστικότητά τους ως προς ΗΟR σε διάλυμα 0.1Μ HClO4 αλλά και σε διάλυμα 0.1Μ ΚΟΗ. Οι ηλεκτροκαταλυτικές σκόνες χαρακτηρίστηκαν φυσικοχημικά με φυσική ρόφηση (ΒΕΤ), XRD, TEM, SEM και XPS. Σε όλες τις περιπτώσεις, έγινε σύγκριση της δραστικότητας των βασισμένων σε Pd ηλεκτροκαταλυτών με εκείνη ηλεκτροκαταλυτών Pt ίδιας συνολικής μεταλλικής φόρτισης. Η αναλογία Pd:M και η θερμοκρασία αναγωγής που χρησιμοποιήθηκαν ήταν οι βέλτιστες από άποψη δραστικότητας, όπως προέκυψε από σχετικά πειράματα αριστοποίησης που έγιναν με τους δραστικότερους για κάθε μελετηθείσα αντίδραση διμεταλλικούς ηλεκτροκαταλύτες. Για κάθε διμεταλλικό σύστημα Pd-M με την μεγαλύτερη δραστικότητα κατά περίπτωση (με μεταλλική φόρτιση 10 wt.%), παρασκευάστηκαν με τη μέθοδο του υγρού εμποτισμού ηλεκτροκαταλύτες ίδιας αναλογίας Pd:Μ και θερμοκρασίας αναγωγής αλλά υψηλότερης μεταλλικής φόρτισης (29 wt.%) των οποίων η δραστικότητα συγκρίθηκε με εκείνη ηλεκτροκαταλυτών Pt ίδιας μεταλλικής φόρτισης. Οι ηλεκτροκαταλύτες με μεταλλική φόρτιση 29 wt.% μελετήθηκαν και ως προς τη σταθερότητά τους. Στην περίπτωση της μελέτης της ORR σε όξινο περιβάλλον και για το δραστικότερο διμεταλλικό σύστημα μελετήθηκε και η επίδραση στη δραστικότητα της μεθόδου σύνθεσης αλλά και του φορέα. Επίσης, στην περίπτωση της ORR σε 0.1Μ ΗClO4, μελετήθηκε και μία σειρά στηριγμένων σε Vulcan XC72R ηλεκτροκαταλυτών 10 wt.% Pt – M (Μ: Ag, Cu, Fe, Ni, Sn, Zn) όσον αφορά τη δραστικότητά τους απουσία και παρουσία αιθανόλης. Τέλος, ο δραστικότερος ως προς ORR σε όξινο περιβάλλον διμεταλλικός ηλεκτροκαταλύτης 22 wt.% Pd – 7 wt.% Zn/C μελετήθηκε ως καθοδικό ηλεκτρόδιο στοιχείου καυσίμου τύπου PEM τροφοδοτούμενου με Η2, του οποίου η απόδοση συγκρίθηκε με εκείνη του ίδιου στοιχείου καυσίμου με κάθοδο βασισμένη σε ηλεκτροκαταλύτες Pt

Performance of a Pd-Zn Cathode Electrode in a H₂ Fueled Single PEM Fuel Cell

A 21.7 wt.% Pd—7.3 wt.% Zn/C electrocatalyst prepared via the wet impregnation (w.i.) method was deposited onto commercial carbon cloth (E-TEK) and tested towards its electrocatalytic performance as a cathode electrode material for oxygen reduction reaction (ORR) in a H2 fueled single proton-exchange membrane fuel cell (PEMFC). A commercial PtRu electrode (E-TEK) was used as PEM anode for hydrogen oxidation reaction (HOR). The performance of the aforementioned PEMFC was compared with that of the same PEMFC with two different Pt-based cathodes, which were prepared by deposition onto commercial carbon cloth (E-TEK) of 29 wt.% Pt/C synthesized via w.i. and of commercial 29 wt.% Pt/C (TKK). The metal loading of the tested cathode electrodes was 0.5 mgmet cm−2. Comparison was based both on polarization curves and on electrochemical impedance spectroscopy (EIS) measurements at varying cell potential. In terms of power density, the lowest and highest performance was exhibited by the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode and the PEMFC with the commercial 29 wt.% Pt/C (TKK) cathode electrode, respectively. This behavior was in accordance with the results of EIS measurements, which showed that the PEMFC with the 21.7 wt.% Pd—7.3 wt.% Zn/C cathode exhibited the highest polarization resistance

Innovative Catalytic Materials for Environmental Remediation and Energy Applications

The need for low-cost and environmentally friendly energy is greater than ever nowadays due to the global population growth as well as the modern lifestyle [...

Recent Trends in Pharmaceuticals Removal from Water Using Electrochemical Oxidation Processes

Nowadays, the research on the environmental applications of electrochemistry to remove recalcitrant and priority pollutants and, in particular, drugs from the aqueous phase has increased dramatically. This literature review summarizes the applications of electrochemical oxidation in recent years to decompose pharmaceuticals that are often detected in environmental samples such as carbamazapine, sulfamethoxazole, tetracycline, diclofenac, ibuprofen, ceftazidime, ciprofloxacin, etc. Similar to most physicochemical processes, efficiency depends on many operating parameters, while the combination with either biological or other physicochemical methods seems particularly attractive. In addition, various strategies such as using three-dimensional electrodes or the electrosynthesis of hydrogen peroxide have been proposed to overcome the disadvantages of electrochemical oxidation. Finally, some guidelines are proposed for future research into the applications of environmental electrochemistry for the degradation of xenobiotic compounds and micropollutants from environmental matrices. The main goal of the present review paper is to facilitate future researchers to design their experiments concerning the electrochemical oxidation processes for the degradation of micropollutants/emerging contaminants, especially, some specific drugs considering, also, the existing limitations of each process

Using Sawdust Derived Biochar as a Novel 3D Particle Electrode for Micropollutants Degradation

This work examined the use of a 3D combined electrochemical process based on particle electrodes from sawdust-derived biochar pyrolized at T = 550–850 °C to remove persistent pollutants. The as-prepared biochar was characterized by scanning electron microscopy with an X-ray energy dispersive spectrometer (SEM/EDS), nitrogen adsorption (BET method) and X-ray diffraction (XRD) techniques. The use of sawdust biochar pyrolized at 650 °C led to a significant increase in efficiency against the sum of conventional 2D electrochemical systems and adsorption, and the synergy index estimated equal to 74.5% at optimum conditions. Sulfamethoxazole (SMX) removal was favored by increasing particle electrode loading. Despite that, the reaction was slightly favored in near-neutral conditions; the system retained most of its activity in the pH range 3–10. The proposed 3D system could degrade different micropollutants, namely SMX, Bisphenol A (BPA), Propylparaben (PP), and Piroxicam (PR). Of particular interest was that no significant reduction in degradation was observed in the case of complex or real water matrices. In addition, the system retained its efficiency regarding SMX removal after five sequential experiments in the 3D combined electrochemical process. However, further investigation is needed to estimate the contribution of the different mechanisms of micropollutant removal in the proposed system

Propane Steam Reforming over Catalysts Derived from Noble Metal (Ru, Rh)-Substituted LaNiO3 and La0.8Sr0.2NiO3 Perovskite Precursors

The propane steam reforming (PSR) reaction was investigated over catalysts derived from LaNiO3 (LN), La0.8Sr0.2NiO3 (LSN), and noble metal-substituted LNMx and LSNMx (M = Ru, Rh; x = 0.01, 0.1) perovskites. The incorporation of foreign cations in the A and/or B sites of the perovskite structure resulted in an increase in the specific surface area, a shift of XRD lines toward lower diffraction angles, and a decrease of the mean primary crystallite size of the parent material. Exposure of the as-prepared samples to reaction conditions resulted in the in situ development of new phases including metallic Ni and La2O2CO3, which participate actively in the PSR reaction. The LN-derived catalyst exhibited higher activity compared to LSN, and its performance for the title reaction did not change appreciably following partial substitution of Ru for Ni. In contrast, incorporation of Ru and, especially, Rh in the LSN perovskite matrix resulted in the development of catalysts with significantly enhanced catalytic performance, which improved by increasing the noble metal content. The best results were obtained for the LSNRh0.1-derived sample, which exhibited excellent long-term stability for 40 hours on stream as well as high propane conversion (XC3H8 = 92%) and H2 selectivity (SH2 = 97%) at 600 °C

Overview of Natural Gas Boiler Optimization Technologies and Potential Applications on Gas Load Balancing Services

Natural gas is a fossil fuel that has been widely used for various purposes, including residential and industrial applications. The combustion of natural gas, despite being more environmentally friendly than other fossil fuels such as petroleum, yields significant amounts of greenhouse gas emissions. Therefore, the optimization of natural gas consumption is a vital process in order to ensure that emission targets are met worldwide. Regarding residential consumption, advancements in terms of boiler technology, such as the usage of condensing boilers, have played a significant role in moving towards this direction. On top of that, the emergence of technologies such as smart homes, Internet of Things, and artificial intelligence provides opportunities for the development of automated optimization solutions, which can utilize data acquired from the boiler and various sensors in real-time, implement consumption forecasting methodologies, and accordingly provide control instructions in order to ensure optimal boiler functionality. Apart from energy consumption minimization, manual and automated optimization solutions can be utilized for balancing purposes, including natural gas demand response, which has not been sufficiently covered in the existing literature, despite its potential for the gas balancing market. Despite the existence of few research works and solutions regarding pure gas DR, the concept of an integrated demand response has been more widely researched, with the existing literature displaying promising results from the co-optimization of natural gas along with other energy sources, such as electricity and heat

Overview of Natural Gas Boiler Optimization Technologies and Potential Applications on Gas Load Balancing Services

Natural gas is a fossil fuel that has been widely used for various purposes, including residential and industrial applications. The combustion of natural gas, despite being more environmentally friendly than other fossil fuels such as petroleum, yields significant amounts of greenhouse gas emissions. Therefore, the optimization of natural gas consumption is a vital process in order to ensure that emission targets are met worldwide. Regarding residential consumption, advancements in terms of boiler technology, such as the usage of condensing boilers, have played a significant role in moving towards this direction. On top of that, the emergence of technologies such as smart homes, Internet of Things, and artificial intelligence provides opportunities for the development of automated optimization solutions, which can utilize data acquired from the boiler and various sensors in real-time, implement consumption forecasting methodologies, and accordingly provide control instructions in order to ensure optimal boiler functionality. Apart from energy consumption minimization, manual and automated optimization solutions can be utilized for balancing purposes, including natural gas demand response, which has not been sufficiently covered in the existing literature, despite its potential for the gas balancing market. Despite the existence of few research works and solutions regarding pure gas DR, the concept of an integrated demand response has been more widely researched, with the existing literature displaying promising results from the co-optimization of natural gas along with other energy sources, such as electricity and heat

Performance of Particulate and Structured Pt/TiO₂-Based Catalysts for the WGS Reaction under Realistic High- and Low-Temperature Shift Conditions

The water–gas shift (WGS) activity of Pt/TiO2-based powdered and structured catalysts was investigated using realistic feed compositions that are relevant to the high-temperature shift (HTS) and low-temperature shift (LTS) reaction conditions. The promotion of the TiO2 support with small amounts of alkali- or alkaline earth-metals resulted in the enhancement of the WGS activity of 0.5%Pt/TiO2(X) catalysts (X = Na, Cs, Ca, Sr). The use of bimetallic (Pt–M)/TiO2 catalysts (M = Ru, Cr, Fe, Cu) can also shift the CO conversion curve toward lower temperatures, but this is accompanied by the production of relatively large amounts of unwanted CH4 at temperatures above ca. 300 °C. Among the powdered catalysts investigated, Pt/TiO2(Ca) exhibited the best performance under both HTS and LTS conditions. Therefore, this material was selected for the preparation of structured catalysts in the form of pellets as well as ceramic and metallic catalyst monoliths. The 0.5%Pt/TiO2(Ca) pellet catalyst exhibited comparable activity with that of a commercial WGS pellet catalyst, and its performance was further improved when the Pt loading was increased to 1.0 wt.%. Among the structured catalysts investigated, the best results were obtained for the sample coated on the metallic monolith, which exhibited excellent WGS performance in the 300–350 °C temperature range. In conclusion, proper selection of the catalyst structure and reaction parameters can shift the CO conversion curves toward sufficiently low temperatures, rendering the Pt/TiO2(Ca) catalyst suitable for practical applications