Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs : Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

The preparation of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) using a very rapid microwave-assisted solvothermal strategy has been described. Electrocatalytic behaviour of the SF-MWCNT-Pd and its ‘mixed’ bimetallic electrocatalysts (i.e., SF-MWCNT-PdSnmix and SF-MWCNT-PdNimix) towards ethanol oxidation in alkaline medium was investigated. The result shows that the mixed Pd-based catalysts (obtained by simple ultrasonic-mixing of the individual MWCNT-metal nanocomposites) gave better electrocatalytic activity than their alloy nanoparticles (obtained by co-reduction of metal salts) or Pd alone. The SF-MWCNT platform gave better electrocatalytic performance compared to the unsulfonated and commercial Vulcan carbons. Detailed electrochemical studies (involving cyclic voltammetry, chronoamperometry, chronopotentiometry, and impedance spectroscopy) prove that the electrocatalytic oxidation of ethanol at the SF-MWCNT-PdNimix platform is more stable, occurs at lower potential, gives lower Tafel slopes, with faster charge-transfer kinetics compared to its SF-MWCNT-PdSnmix counterpart. Also, result revealed that SF-MWCNT-PdNimix is more tolerant to CO poisoning than the SF-MWCNT-PdSnmix. The results provide some important insights into the electrochemical response of microwave-synthesised Pd-based bimetallic catalysts for potential application in direct ethanol alkaline fuel cell technology.The CSIR and NRF.http://www.elsevier.com/locate/electact

Porous multi-metallic Pt-based nanostructures as efficient electrocatalysts for ethanol oxidation: A mini-review

Porous multi-metallic Pt-based nanostructures (PM-Pt-Ns) electrocatalysts possess various unique structural and compositional merits that facilitate their utilization in ethanol oxidation reaction (EOR), which is one of the most important parameters in ethanol-based fuel cells. Improving the EOR activity of PM-Pt-Ns electrocatalysts with low Pt-content remains a daunting challenge, so various efforts devoted to overcoming these barriers lie in controlling nanoparticle shapes/compositions using a variety of methods. This mini-review evaluates the most interesting papers related to PM-Pt-Ns (i.e., binary and ternary) electrocatalysts for EOR with annotations in the last three years. Different preparation methods, morphologies and compositions of PM-Pt-Ns electrocatalysts on the EOR activity are discussed, as well as the challenges for scalable fabrication of PM-Pt-Ns electrocatalysts as anodes for practical ethanol-based fuel cells. Finally, the prospects for directing the development of novel PM-Pt-Ns for practical applications are emphasized

Electrocatalytic oxidation of ethylene glycol at palladium-bimetallic nanocatalysts (PdSn and PdNi) supported on sulfonate-functionalised multi-walled carbon nanotubes

Electrocatalytic oxidation of ethylene glycol (EG) in alkaline medium using nano-scaled palladium-based bimetallic catalysts (PdM, where M = Ni and Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) is compared. The bimetallic mixture (i.e., SF-MWCNT–PdSnmix and SF-MWCNT–PdNimix) showed better electrocatalysis towards EG oxidation than the SF-MWCNT–Pd. At the SF-MWCNT– PdSnmix platform, oxidation of EG occurred at lower onset and peak potentials, higher current density, and faster kinetics (lower impedance) than at the SF-MWCNT–PdNimix platform. EG oxidation at the SF-MWCNT–PdNimix is more stable than at the SF-MWCNT–PdSnmix. Indeed, Sn is a more favoured cocatalyst with Pd in EG electro-oxidation.CSIR and NRFhttp://www.elsevier.com/locate/jelechemhb201

Porous high-entropy alloys as efficient electrocatalysts for water-splitting reactions

Porous high-entropy alloys (HEAs) have emerged as promising electrocatalysts for water-splitting reactions, owing to their rich dissimilar active sites, elemental diversity, and multiple functionalities. The rational design of HEAs for water-splitting attracted great interest in improving their current performance, so it is essential to provide timely updates on this field. This review emphasizes the preparation methods of porous HEAs and the effect of their salient features like high configurational entropy, cocktail effect, lattice distortion, and sluggish diffusion on oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). This mini-review also provides some insights into the current limitations and future perspectives to direct research on the development of ideal HEAs for OER and HER

Efforts at Enhancing Bifunctional Electrocatalysis and Related Events for Rechargeable Zinc-Air Batteries

Invited for this month's cover picture is the group of Prof. Dr. Kenneth I. Ozoemena at the University of the Witwatersrand and collaborators from Qatar University and Peking University. The Front Cover illustrates the significance of bifunctional electrocatalysis (ORR / OER) and zinc anode as the key drivers for the development of rechargeable zinc-air batteries that promise to revolutionize electricity storage and applications (represented herein as electric vehicle charging point). Read the full text of the Review at 10.1002/celc.202100574

Carbon nanotube-enhanced photoelectrochemical properties of metallo-octacarboxyphthalocyanines

The photoelectrochemistry of metallo-octacarboxyphthalocyanines (MOCPc, where M = Zn or Si(OH)2) integrated with MWCNTs for the development of dye-sensitized solar cells (DSSCs) is reported. The DSSC performance (obtained from the photo-chronoamperometric and photo-impedimetric data) decreased as ZnOCPc > (OH)2SiOCPc. The incorporation of the MWCNTs on the surface of the TiO2 film (MOCPc–MWCNT systems) gave higher photocurrent density than the bare MOCPc complexes. Also, from the EIS results, the MOCPc–MWCNT hybrids gave faster charge transport kinetics (approximately three times faster) compared to the bare MOCPc complexes. The electron lifetime was slightly longer (ca. 6 ms) at the ZnOCPc systems than at the (OH)2SiOCPc system (ca. 4 ms) meaning that the presence of the MWCNTs on the surface of the TiO2 film did not show any significant improvement on preventing charge recombination process

Pd-Nanoparticles Embedded Metal-Organic Framework-Derived Hierarchical Porous Carbon Nanosheets as Efficient Electrocatalysts for Carbon Monoxide Oxidation in Different Electrolytes

Rational synthesis of Co-ZIF-67 metal-organic framework (MOF)-derived carbon-supported metal nanoparticles is essential for various energy and environmental applications; however, their catalytic activity toward carbon monoxide (CO) oxidation in various electrolytes is not yet emphasized. Co-ZIF-67-derived hierarchical porous carbon nanosheet-supported Pd nanocrystals (Pd/ZIF-67/C) were prepared using a simple microwave-irradiation approach followed by carbonization and etching. Mechanistically, during microwave irradiation, triethyleneamine provides abundant reducing gases that promote the formation of Pd nanoparticles/Co-Nxin porous carbon nanosheets with the assistance of ethylene glycol and also form a multimodal pore size. The electrocatalytic CO oxidation activity and stability of Pd/ZIF-67/C outperformed those of commercial Pd/C and Pt/C catalysts by (4.2 and 4.4, 4.0 and 2.7, 3.59 and 2.7) times in 0.1 M HClO4, 0.1 M KOH, and 0.1 M NaHCO3, respectively, due to the catalytic properties of Pd besides the conductivity of Co-Nxactive sites and delicate porous structures of ZIF-67. Notably, using Pd/ZIF-67/C results in a higher CO oxidation activity than Pd/C and Pt/C. This study may pave the way for using MOF-supported multi-metallic nanoparticles for CO oxidation electrocatalysis. 2022 American Chemical Society. All rights reserved.This work was supported by the Qatar University Internal Grant (QUHI-CAM-22/23-550), Qatar National Research Fund (NPRP13S-0117-200095), and NRF/DSI/Wits SARChI Chair in Materials Electrochemistry and Energy Technologies (MEET) (UID No. 132739). The authors are grateful to the Environmental Science Center (ESC), Qatar University for the ICP-OES analysis.Scopu

Porous spinel-type transition metal oxide nanostructures as emergent electrocatalysts for oxygen reduction reactions

Porous spinel-type transition metal oxide (PS-TMO) nanocatalysts comprising two kinds of metal (denoted as AxB3−xO4, where A, B = Co, Ni, Zn, Mn, Fe, V, Sm, Li, and Zn) have emerged as promising electrocatalysts for oxygen reduction reactions (ORRs) in energy conversion and storage systems (ECSS). This is due to the unique catalytic merits of PS-TMOs (such as p-type conductivity, optical transparency, semiconductivity, multiple valence states of their oxides, and rich active sites) and porous morphologies with great surface area, low density, abundant transportation paths for intermediate species, maximized atom utilization and quick charge mobility. In addition, PS-TMOs nanocatalysts are easily prepared in high yield from Earth-abundant and inexpensive metal precursors that meet sustainability requirements and practical applications. Owing to the continued developments in the rational synthesis of PS-TMOs nanocatalysts for ORRs, it is utterly imperative to provide timely updates and highlight new advances in this research area. This review emphasizes recent research advances in engineering the morphologies and compositions of PS-TMOs nanocatalysts in addition to their mechanisms, to decipher their structure-activity relationships. Also, the ORR mechanisms and fundamentals are discussed, along with the current barriers and future outlook for developing the next generation of PS-TMOs nanocatalysts for large-scale ECSS