Energy-Efficient Rational Designing of Multifunctional Nanocomposites by Preferential Anchoring of Metal Ions via Fermi Level Positioning of Carbon Nanostructures

Microwave-Assisted Synthesis of Platinum-free High-Entropy Alloy Catalysts on Reduced Graphene Oxide Sheets for Enhanced Oxygen Reduction and Evolution Reactions

Nano-sized high-entropy materials (HEMs) recently received more attention to researchers due to their superior electrochemical catalytic properties. HEMs comprise at least five elements with or without metals and are synthesized through solid-state reactions and solution-mediated techniques. The presence of many elements in these HEMs result in a high mixing entropy and facilitates the formation of stable solid solutions in fundamental crystal structures. Herein, Pt-free high-entropy alloys (HEAs) were synthesized through facile and straightforward pulse microwave (PM) synthesis technique, which serve as efficient electrochemical catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The PM synthesis method was conducted at an extremely low temperature (100 °C) without any external catalytic reagents. Using this PM technique, Cr18.2Zr13.5Ti5.3Co17.8Ni8.4Cu8.5Fe28.3 and Al15.3Mn18.2Ti3.7Co23.2Ni5.9Cu5.9Fe27.8 HEAs catalysts were synthesized with superior catalytic activity towards OER and ORR and compare its activities with pure Pt catalysts. The as-prepared HEAs also display an anti-CO poisoning effect and long-term durability, as compared to pure Pt catalysts. The low-temperature PM approach not only confirms the feasibility of synthesis of noble metal-free HEAs but also validates their superior catalytic activity towards OER and ORR, which is beneficial for the development of proton exchange membrane fuel cells and proton exchange membrane water electrolysis.

Tailored Design of Mesoporous Nanospheres with High Entropic Alloy Sites for Efficient Redox Electrocatalysis

High Entropy Alloys (HEAs) are a versatile material with unique properties, tailored for various applications. They enable pH-sensitive electrocatalytic transformations like hydrogen evolution reaction (HER) and hydrogen oxidation reactions (HOR) in alkaline media. Mesoporous nanostructures with high surface area are preferred for these electrochemical reactions, but designing mesoporous HEA sis challenging. To overcome this challenge, a low-temperature triblock copolymer-assisted wet-chemical approach is developed to produce mesoporous HEA nanospheres composed of PtPdRuMoNi systems with sufficient entropic mixing. Owing to active sites with inherent entropic effect, mesoporous features, and increased accessibility, optimized HEA nanospheres promote strong HER/HOR performance in alkaline medium. At 30 mV nominal overpotential, it exhibits a mass activity of ≈167 (HER) and 151 A gPt -1 (HOR), far exceeding commercial Pt-C electrocatalysts (34 and 48 A gPt -1) and many recently reported various alloys. The Mott-Schottky analysis reveals HEA nanospheres inherit high charge carrier density, positive flat band potential, and smaller charge transfer barrier, resulting in better activity and faster kinetics. This micelle-assisted synthetic enable the exploration of the compositional and configurational spaces of HEAs at relatively low temperature, while simultaneously facilitating the introduction of mesoporous nanostructures for a wide range of catalytic applications.

Self-Assembled Nanocomposites and Nanostructures for Environmental and Energic Applications

With the rapid development of nanotechnology, nanocomposites and nanostructures have attracted significant attention due to their unique physical and chemical properties and variable functionalities [...].

FeCoNiMnCr High-Entropy Alloy Nanoparticle-Grafted NCNTs with Promising Performance in the Ohmic Polarization Region of Fuel Cells

We report a user-friendly methodology for the successful designing of targeted single-phased face-centered cubic (fcc) FeCoNiMnCr high-entropy alloy (HEA) nanoparticle-grafted N-doped carbon nanotubes (CNTs). The nanostructure assimilates the advantages of N-doped carbon and HEA nanoparticles as a core for the efficient promotion of electrochemical oxygen reduction reaction (ORR). It emulates the commercial Pt-C electrocatalyst for ORR and shows promise for better performance in the Ohmic polarization region of fuel cells. In addition, it ensures superior efficacy over those of numerous recently reported transition metal-based traditional alloy composites for ORR. The presented methodology has the potential to pave the way for the effective designing of a variety of targeted HEA systems with ease, which is necessary to widen the domain of HEA for numerous applications.

A novel sensitive ACNTs-MoO2 SERS substrate boosted by synergistic enhancement effect

Integrating chemical enhancement (CM) and electromagnetic enhancement (EM) into one substrate is of great significance, but as far as we know, little research has been done on this project. In this paper, the novel bead chain like acidified carbon nanotubes-MoO₂ (ACNTs-M) were designed by a simple two-step hydrothermal synthesis method. Benefitting from a good adsorption capacity, chemical enhancement and surface electromagnetic field enhancement effect, ACNTs-M exhibits a stunning SERS performance. The maximum enhancement factor (EF) of 5.13 × 10⁷ is obtained with R6G molecules on ACNTs-M. The limit of detection (LOD) of R6G is 10^-10 M. In addition, ACNTs-M also exhibits SERS sensitivity of other organic dyes (CV, RhB and MB). The results of Raman signal enhancement mechanism research verified that the synergy of CM and EM is the reason for the high SERS sensitivity of ACNTs-M. We believe that our work may bring cutting edge of development of stable and highly sensitive nonmetal SERS substrates.

Atomic Arrangement Modulation in CoFe Nanoparticles Encapsulated in N-Doped Carbon Nanostructures for Efficient Oxygen Reduction Reaction

The properties and, hence, the application of materials are dependent on the way their constituent atoms are arranged. Here, we report a facile approach to produce body-centered cubic (bcc) and face-centered cubic (fcc) phases of bimetallic FeCo crystalline nanoparticles embedded into nitrogen-doped carbon nanotubes (NCNTs) with equal loading and almost similar particle size for both crystalline phases by a rational selection of precursors. The two electrocatalysts with similar composition but different crystalline structures of the encapsulated nanoparticles have allowed us, for the first time, to account for the effect of crystal structure on the overall work function of electrocatalysts and the concomitant correlation with the oxygen reduction reaction (ORR). This study unveils that the electrocatalysts with lower work function show lower activation energy to facilitate the ORR. Importantly, the difference between the ORR activation energy on electrocatalysts and their respective work functions are found to be identical (∼0.2 eV). A notable decrease in the ORR activity after acid treatment indicates the significant role of encapsulated FeCo nanoparticles in influencing the oxygen electrochemistry by modulating the material property of overall electrocatalysts.

Ruthenium nanodendrites on reduced graphene oxide: an efficient water and 4-nitrophenol reduction catalyst

A green and efficient protocol is reported for the elegant design of reduced graphene oxide (rGO)-supported Ru nanodendrites for promotion of electrochemical water reduction in a wide pH range as well as for environmental remediation.