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In this study, we explored the surface modification of a glassy carbon electrode through the electrografting of 4-Aminophenyl phosphate, which features heteroatoms and ionic properties. The electrochemical grafting process involves reducing in situ-generated diazonium derivatives. The primary objective of this research was to immobilize organic layers and assess their electrochemical and surface properties. Subsequently, the generated surface serves as a template for the electrochemical growth of Pd and Co nanoparticles on functionalized electrodes. The electrocatalytic performances of these hybrid electrodes in driving the hydrogen evolution reaction were investigated. The obtained results indicate an enhancement in the electrocatalytic activity of the modified electrodes, where lower overpotential and higher stability were observed when the catalyst was electrodeposited onto the attached ionic layer. These findings highlight the synergistic effect between the attached phenyl phosphate moieties and electrocatalysts. [ABSTRACT FROM AUTHOR]

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 (PtCF3 ${{_{{\rm CF}{_{3}}}}}$ NPs/C) are compared to commercial benchmark PtNPs/C. PtCF3 ${{_{{\rm CF}{_{3}}}}}$ 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Intensive research into the design of catalysts involved in energy conversion and fuel cell technologies has allowed great progress in the field. However, durable, efficient and selective electrocatalytic systems for the activation of fuel molecules at the lowest cost are still needed. The most developed strategies consist of tailoring the shape, size and composition of metallic nanomaterials. Yet, deliberate surface modification of the catalysts should be considered as a promising alternative approach. The functionalization of metallic catalysts with organic ligands has been recently demonstrated to promote high catalytic activity. This Review focuses on the functionalization of metallic or alloy catalysts with organic ligands, showing the impact of the surface modification for different materials and different reactions. Hybrid systems based on this alternative strategy could contribute to the elaboration of cutting‐edge systems for electrocatalysis. [ABSTRACT FROM AUTHOR]

Environmental context: The origin of organic matter at Earth's continental surface can be either terrestrial or microbial, and its precise composition can influence its reactivity towards metals. We investigated the potential of rare earth elements to fingerprint the origin of various organic matters through their reactivity and composition. The rare earth element patterns can be useful tools to determine the reactivity and also pristine source of natural organic matter. Rare earth elements (REEs) have been shown to be efficient tracers of the functional sites and/or complexes formed on humic molecules. In the present study, we test the potential of REEs to be used as tracers of the sources of humic substances (HSs). Three types of organic matter (OM) of terrestrial and microbiological origin were tested. The experiments of REEs binding to the HSs were combined with size-fractionation experiments. The REE patterns were the most fractionated in the <10 kDa fraction. For Leonardite humic acid (LHA) and Aldrich humic acid (AHA), the REE patterns were consistent with the REEs binding to strong but low density sites for a low REE/C loading. By contrast, for Pony Lake fulvic acid (PLFA), the REE pattern was similar to the REE pattern developed onto a bacteria cell surface and was attributed to the REEs binding to phosphate surface sites. Fluorescence and elemental analysis of PLFA showed that the <10 kDa fraction was the fraction with the stronger microbiological character, which suggested the REEs were probably bound to PLFA through REE-phosphate complexes. Such results therefore provide a new possibility for the use of REEs to assess an OM source without the need to perform numerous or complex analytical methodologies. Environmental context. The origin of organic matter at Earth's continental surface can be either terrestrial or microbial, and its precise composition can influence its reactivity towards metals. We investigated the potential of rare earth elements to fingerprint the origin of various organic matters through their reactivity and composition. The rare earth element patterns can be useful tools to determine the reactivity and also pristine source of natural organic matter. [ABSTRACT FROM AUTHOR]

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., (Copyright © 2020 Mattiuzzi, Lenne, Carvalho Padilha, Troian-Gautier, Leroux, Jabin and Lagrost.)