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A conceptual challenge toward more versatile direct methanol fuel cell (DMFC) is the design of a single material electrocatalyst with high activity and durability for both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). This requires to conciliate methanol tolerance not to hinder ORR at the cathode with a good MOR activity at the anode. This is especially incompatible with Pt materials. We tackled this challenge by deriving a supramolecular concept where surface-grafted molecular ligands regulate the Pt-catalyst reactivity. ORR and MOR activities of newly reported Pt-calix[4]arenes nanocatalysts (PtCF3NPs/C) are compared to commercial benchmark PtNPs/C. PtCF3NPs/C exhibit a remarkable methanol tolerance without losing the MOR reactivity along with outstanding durability and chemical stability. Beyond designing single-catalyst material, operable in DMFC cathodic and anodic compartments, the results highlight a promising strategy for tuning interfacial properties.

A conceptual challenge toward more versatile direct methanol fuel cells (DMFCs) is the design of a single material electrocatalyst with high activity and durability for both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). This requires to conciliate methanol tolerance not to hinder ORR at the cathode with a good MOR activity at the anode. This is especially incompatible with Pt materials. We tackled this challenge by deriving a supramolecular concept where surface‐grafted molecular ligands regulate the Pt‐catalyst reactivity. ORR and MOR activities of newly reported Pt‐calix[4]arenes nanocatalysts (Pt NPs/C) are compared to commercial benchmark PtNPs/C. Pt NPs/C exhibit a remarkable methanol tolerance without losing the MOR reactivity along with outstanding durability and chemical stability. Beyond designing single‐catalyst material, operable in DMFC cathodic and anodic compartments, the results highlight a promising strategy for tuning interfacial properties., SCOPUS: ar.j, info:eu-repo/semantics/published

A series of surface-functionalized gold nanocatalysts are synthesized. Through diazonium chemistry, calix[4]arene molecules are grafted at the gold surface. Sharing the same anchoring function and a common backbone, the calix[4]arene ligands possess distinct terminal chemical functions where the length, hydrophobic nature, and oxygen affinity are varied. Thanks to the versatility of the calix[4]arene platform, this paper only focuses on the molecular tuning of the solid/liquid interface through the change of the tail groups while electronic effects that are regulated by the anchoring function will be similar for all catalysts. Electrocatalytic tests demonstrate the influence of the tails group on the oxygen reduction reaction performances, including efficiency, selectivity, and durability. Beyond a pure geometric steric effect, it is shown that chemical properties of the ligands can effectively tune the interactions between the metallic catalyst and the electrolyte and reactants., SCOPUS: ar.j, info:eu-repo/semantics/published

Silver nanoparticles (AgNPs) were deliberately functionalized via aryl diazonium chemistry with a monolayer of calix[4]arenes. The resulting nanohybrids show high efficiency and high selectivity toward the ORR in alkaline media along with an exceptional durability and a high methanol tolerance., SCOPUS: ar.j, info:eu-repo/semantics/published

Pioneered by J. Pinson and coll. in 1990s, the reductive grafting of aryldiazonium salts has become a powerful method for surface functionalization. Highly robust interfaces result from this surface attachment, resistant to heat, chemical degradation and ultrasonication. Importantly, this approach can be applied to many materials, ranging from conducting, semi-conducting, oxides to insulating substrates. In addition, either massive, flat surfaces or nanomaterials can be functionalized. The method is easy to process and fast. The grafting process involves the formation of highly reactive aryl radicals able to attack the substrate. However, the generated radicals can also react with already-grafted aryl species, leading to the formation of loosely-packed polyaryl multilayer films, typically of 10–15 nm thick. It is thus highly challenging to control the vertical extension of the deposited layer and to form well-ordered monolayers from aryldiazonium salts. In this mini review, we briefly describe the different strategies that have been developed to prepare well-ordered monolayers. We especially focus on two strategies successfully used in our laboratories, namely the use of unconventional solvents, i.e., room temperature ionic liquids (RTILs), as grafting media and the use of calixarene macrocycles by taking benefit of their pre-organized structure. These strategies give large possibilities for the structuring of interfaces with the widest choice of materials and highlight the potential of aryldiazonium grafting as a competitive alternative to self-assembled monolayers (SAMs) of alkyl thiols.

The (electro)chemical grafting of a polyfluorinated calix[4]arene on gold, polypropylene and glass is reported. The modified surfaces were characterized by ellipsometry, atomic force microscopy (AFM), and by X-ray photoelectron spectroscopy (XPS). A nanometric, robust and uniform monolayer of covalently surface-bound calix[4]arenes was obtained on the three different materials. For all surfaces, contact angles higher than 110° were recorded, highlighting the hydrophobic character given by this ∼2 nm thin organic monolayer. Remarkably, the contact angle values remained unchanged after 18 months under a laboratory atmosphere. The results presented herein thus present an attractive and sustainable strategy for bringing hydrophobic properties to the interface of a wide range of materials.

The deliberate surface modification of nanocatalysts with organic ligands has recently emerged as a promising strategy to boost their efficiency, durability, and/or selectivity in key electrocatalytic processes. The interface between the metallic interface and the immobilized ligands promotes high electrocatalytic activity. Herein, the oxygen reduction reaction activity of gold nanoparticles functionalized with a covalently bound monolayer of calix[4]arenes is compared with commercially available gold nanoparticles, classically stabilized through electrostatic adsorption of citrates onto the gold surfaces. Nanocatalysts coated by calix[4]arenes show enhanced selectivity and stability compared to their citrate-stabilized counterparts. These nanohybrids exhibit excellent activity with a dominant 4-electron reduction of O2 with good electrocatalytic performances along with a high robustness under operation as revealed by X-ray photoelectron spectroscopy analyses., SCOPUS: ar.j, info:eu-repo/semantics/published

Pioneered by J. Pinson and coll. in 1990s, the reductive grafting of aryldiazonium salts has become a powerful method for surface functionalization. Highly robust interfaces result from this surface attachment, resistant to heat, chemical degradation and ultrasonication. Importantly, this approach can be applied to many materials, ranging from conducting, semi-conducting, oxides to insulating substrates. In addition, either massive, flat surfaces or nanomaterials can be functionalized. The method is easy to process and fast. The grafting process involves the formation of highly reactive aryl radicals able to attack the substrate. However, the generated radicals can also react with already-grafted aryl species, leading to the formation of loosely-packed polyaryl multilayer films, typically of 10–15 nm thick. It is thus highly challenging to control the vertical extension of the deposited layer and to form well-ordered monolayers from aryldiazonium salts. In this mini review, we briefly describe the different strategies that have been developed to prepare well-ordered monolayers. We especially focus on two strategies successfully used in our laboratories, namely the use of unconventional solvents, i.e. room temperature ionic liquids (RTILs), as grafting media and the use of calixarene macrocycles by taking benefit of their pre-organized structure. These strategies give large possibilities for the structuring of interfaces with the widest choice of materials and highlight the potential of aryldiazonium grafting as a competitive alternative to self-assembled monolayers (SAMs) of alkyl thiols., SCOPUS: re.j, info:eu-repo/semantics/published

The grafting of a polyfluorinated calix[4]arene-tetradiazonium derivative on various surfaces led to the formation of very robust and stable hydrophobic monolayers., The (electro)chemical grafting of a polyfluorinated calix[4]arene on gold, polypropylene and glass is reported. The modified surfaces were characterized by ellipsometry, atomic force microscopy (AFM), and by X-ray photoelectron spectroscopy (XPS). A nanometric, robust and uniform monolayer of covalently surface-bound calix[4]arenes was obtained on the three different materials. For all surfaces, contact angles higher than 110° were recorded, highlighting the hydrophobic character given by this ∼2 nm thin organic monolayer. Remarkably, the contact angle values remained unchanged after 18 months under a laboratory atmosphere. The results presented herein thus present an attractive and sustainable strategy for bringing hydrophobic properties to the interface of a wide range of materials., info:eu-repo/semantics/published