Carbon Monoxide Tolerant Pt-Based Electrocatalysts for H2-PEMFC Applications: Current Progress and Challenges

The activity degradation of hydrogen-fed proton exchange membrane fuel cells (H2-PEMFCs) in the presence of even trace amounts of carbon monoxide (CO) in the H2 fuel is among the major drawbacks currently hindering their commercialization. Although significant progress has been made, the development of a practical anode electrocatalyst with both high CO tolerance and stability has still not occurred. Currently, efforts are being devoted to Pt-based electrocatalysts, including (i) alloys developed via novel synthesis methods, (ii) Pt combinations with metal oxides, (iii) core–shell structures, and (iv) surface-modified Pt/C catalysts. Additionally, the prospect of substituting the conventional carbon black support with advanced carbonaceous materials or metal oxides and carbides has been widely explored. In the present review, we provide a brief introduction to the fundamental aspects of CO tolerance, followed by a comprehensive presentation and thorough discussion of the recent strategies applied to enhance the CO tolerance and stability of anode electrocatalysts. The aim is to determine the progress made so far, highlight the most promising state-of-the-art CO-tolerant electrocatalysts, and identify the contributions of the novel strategies and the future challenges. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.The authors thankfully acknowledge co-financing from the European Union and Greek national funds through the Operational Program for Competitiveness, Entrepreneurship, and Innovation, under the program RESEARCH-CREATE-INNOVATE (Project code: T1EDK-02442)

Cost Effective Synthesis of Graphene Nanomaterials for Non-Enzymatic Electrochemical Sensors for Glucose: A Comprehensive Review

The high conductivity of graphene material (or its derivatives) and its very large surface area enhance the direct electron transfer, improving non-enzymatic electrochemical sensors sensitivity and its other characteristics. The offered large pores facilitate analyte transport enabling glucose detection even at very low concentration values. In the current review paper we classified the enzymeless graphene-based glucose electrocatalysts’ synthesis methods that have been followed into the last few years into four main categories: (i) direct growth of graphene (or oxides) on metallic substrates, (ii) in-situ growth of metallic nanoparticles into graphene (or oxides) matrix, (iii) laser-induced graphene electrodes and (iv) polymer functionalized graphene (or oxides) electrodes. The increment of the specific surface area and the high degree reduction of the electrode internal resistance were recognized as their common targets. Analyzing glucose electrooxidation mechanism over Cu-Co-and Ni-(oxide)/graphene (or derivative) electrocatalysts, we deduced that glucose electrochemical sensing properties, such as sensitivity, detection limit and linear detection limit, totally depend on the route of the mass and charge transport between metal(II)/metal(III); and so both (specific area and internal resistance) should have the optimum values. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Asst. Prof. Brouzgou, A., thankfully acknowledges the Research, Innovation and Excellence Structure (DEKA) of the University of Thessaly for the funding of the research program entitled: ‘Electrochemical (bio)sensors: synthesis of novel carbon monolayer-based nanoelectrodes for biomolecules detection’ and Ms Balkourani, G. (PhD student) thankfully acknowledges the Hellenic Foundation for Research and Innovation (HFRI), the PhD Fellowship grant. 25, 6816

Fundamentals and Principles of Solid-State Electrochemical Sensors for High Temperature Gas Detection

The rapid development of science, technology, and engineering in the 21st century has offered a remarkable rise in our living standards. However, at the same time, serious environmental issues have emerged, such as acid rain and the greenhouse effect, which are associated with the ever-increasing need for energy consumption, 85% of which comes from fossil fuels combustion. From this combustion process, except for energy, the main greenhouse gases-carbon dioxide and steam-are produced. Moreover, during industrial processes, many hazardous gases are emitted. For this reason, gas-detecting devices, such as electrochemical gas sensors able to analyze the composition of a target atmosphere in real time, are important for further improving our living quality. Such devices can help address environmental issues and inform us about the presence of dangerous gases. Furthermore, as non-renewable energy sources run out, there is a need for energy saving. By analyzing the composition of combustion emissions of automobiles or industries, combustion processes can be optimized. This review deals with electrochemical gas sensors based on solid oxide electrolytes, which are employed for the detection of hazardous gasses at high temperatures and aggressive environments. The fundamentals, the principle of operation, and the configuration of potentiometric, amperometric, combined (amperometric-potentiometric), and mixed-potential gas sensors are presented. Moreover, the results of previous studies on carbon oxides (COx), nitrogen oxides (NOx), hydrogen (H2), oxygen (O2), ammonia (NH3), and humidity (steam) electrochemical sensors are reported and discussed. Emphasis is given to sensors based on oxygen ion and proton-conducting electrolytes. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Fotini Tzorbatzoglou, Costas Molochas, and Panagiotis Tsiakaras thankfully acknowledge co-financing from the European Union and Greek national funds through the Operational Program for Competitiveness, Entrepreneurship, and Innovation, under program RESEARCH-CREATE-INNOVATE (Project code: T1EDK-02442)

Emerging materials for the electrochemical detection of COVID-19

The SARS-CoV-2 virus is still causing a dramatic loss of human lives worldwide, constituting an unprecedented challenge for the society, public health and economy, to overcome. The up-to-date diagnostic tests, PCR, antibody ELISA and Rapid Antigen, require special equipment, hours of analysis and special staff. For this reason, many research groups have focused recently on the design and development of electrochemical biosensors for the SARS-CoV-2 detection, indicating that they can play a significant role in controlling COVID disease. In this review we thoroughly discuss the transducer electrode nanomaterials investigated in order to improve the sensitivity, specificity and response time of the as-developed SARS-CoV-2 electrochemical biosensors. Particularly, we mainly focus on the results appeard on Au-based and carbon or graphene-based electrodes, which are the main material groups recently investigated worldwidely. Additionally, the adopted electrochemical detection techniques are also discussed, highlighting their pros and cos. The nanomaterial-based electrochemical biosensors could enable a fast, accurate and without special cost, virus detection. However, further research is required in terms of new nanomaterials and synthesis strategies in order the SARS-CoV-2 electrochemical biosensors to be commercialized. © 2021 Elsevier B.V

Hierarchically Skeletal Multi-layered Pt-Ni Nanocrystals for Highly Efficient Oxygen Reduction and Methanol Oxidation Reactions

Pt based materials are the most efficient electrocatalysts for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in fuel cells. Maximizing the utilization of Pt based materials by modulating their morphologies to expose more active sites is a fundamental objective for the practical application of fuel cells. Herein, we report a new class of hierarchically skeletal Pt-Ni nanocrystals (HSNs) with a multi-layered structure, prepared by an inorganic acid-induced solvothermal method. The addition of H2SO4 to the synthetic protocol provides a critical trigger for the successful growth of Pt-Ni nanocrystals with the desired structure. The Pt-Ni HSNs synthesized by this method exhibit enhanced mass activity of 1.25 A mgpt−1 at 0.9 V (versus the reversible hydrogen electrode) towards ORR in 0.1-M HClO4, which is superior to that of Pt-Ni multi-branched nanocrystals obtained by the same method in the absence of inorganic acid; it is additionally 8.9-fold higher than that of the commercial Pt/C catalyst. Meanwhile, it displays enhanced stability, with only 21.6% mass activity loss after 10,000 cycles (0.6–1.0 V) for ORR. Furthermore, the Pt-Ni HSNs show enhanced activity and anti-toxic ability in CO for MOR. The superb activity of the Pt-Ni HSNs for ORR and MOR is fully attributed to an extensively exposed electrochemical surface area and high intrinsic activity, induced by strain effects, provided by the unique hierarchically skeletal alloy structure. The novel open and hierarchical structure of Pt-Ni alloy provides a promising approach for significant improvements of the activity of Pt based alloy electrocatalysts. © 2021 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences.This work was supported by the National Key Research and Development Plan (2017YFB0103001), the link project of the National Natural Science Foundation of China and Fujian Province (U1705252), the Guangxi Science and Technology Projects (AA17204083, AB16380030), the innovation project of Guangxi Graduate Education (YCBZ2019012)

Nanostructure Engineering of Metal–Organic Derived Frameworks: Cobalt Phosphide Embedded in Carbon Nanotubes as an Efficient Orr Catalyst

Heteroatom doping is considered an efficient strategy when tuning the electronic and structural modulation of catalysts to achieve improved performance towards renewable energy applications. Herein, we synthesized a series of carbon-based hierarchical nanostructures through the controlled pyrolysis of Co-MOF (metal organic framework) precursors followed by in situ phosphidation. Two kinds of catalysts were prepared: metal nanoparticles embedded in carbon nanotubes, and metal nanoparticles dispersed on the carbon surface. The results proved that the metal nanoparticles embedded in carbon nanotubes exhibit enhanced ORR electrocatalytic performance, owed to the enriched catalytic sites and the mass transfer facilitating channels provided by the hierarchical porous structure of the carbon nanotubes. Furthermore, the phosphidation of the metal nanoparticles embedded in carbon nanotubes (P-Co-CNTs) increases the surface area and porosity, resulting in faster electron transfer, greater conductivity, and lower charge transfer resistance towards ORR pathways. The P-Co-CNT catalyst shows a half-wave potential of 0.887 V, a Tafel slope of 67 mV dec−1, and robust stability, which are comparatively better than the precious metal catalyst (Pt/C). Conclusively, this study delivers a novel path for designing multiple crystal phases with improved catalytic performance for energy devices. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Acknowledgments: S.S.A. Shah is grateful to the higher education commission (HEC) of Pakistan for IPFP funding at the Institute of Chemistry, The Islamia University of Bahawalpur, Pakistan. Furthermore, P. Tsiakaras, A. Brouzgou and C. Molochas thankfully acknowledge the co-financing by the European Union & Greek National funds through the Operational Program Competitiveness, Entrepreneurship, and Innovation, under the call RESEARCH–CREATE–INNOVATE (T1EDK-02442)

PtM/C (M = Sn, Ru, Pd, W) based anode direct ethanol-PEMFCs: Structural characteristics and cell performance

In the present work, the role of the structural characteristics of Pt-based catalysts on the single direct ethanol proton exchange membrane fuel cell (PEMFC) performance is examined. Several PtM/C (M = Sn, Ru, Pd, W) catalysts were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD) and then evaluated as anode catalysts in single direct ethanol fuel cells. XRD spectra showed that Pt lattice parameter decreases with the addition of Ru or Pd and increases with the addition of Sn or W. According to the obtained experimental results, PtSn catalysts presented better electrocatallytic activity towards ethanol electro-oxidation. Based on these results, PtSn/C catalysts with different Pt/Sn atomic ratio were tested and compared. The maximum power density values obtained were correlated with the structural characteristics of the catalysts. A volcano type behaviour between the fuel cell maximum power density and the corresponding atomic percentage of Sn (Sn%) was observed. It was also observed that Sn% affects almost linearly the PtxSny, catalysts' lattice parameter. (C) 2007 Elsevier B.V. All rights reserved