Search

This article reveals the promising potential of MnCoOx solid solutions as an effective catalyst for the oxygen evolution reaction (OER). The solid oxide solution was synthesized by utilizing redox deposition of KMnO4 and Co(NO3)2 on a carbon paper (CP) support with varying Co/Mn ratios. XRD and TEM analyses confirmed the homogeneous distribution of Co and Mn species in MnCoOx. According to OER tests in acid electrolyte, the catalytic efficiency of Mn1Co5Ox surpassed that of Co3O4, MnOx, and IrO2, demonstrating overpotentials of 275 and 569 mV at a current density of 10 and 100 mA cm−2, respectively. The investigation emphasizes the crucial roles of Co3+ and Mn4+ cations as well as oxygen vacancies (Ov) sites in facilitating the OER mechanism. These essential characteristics were duly observed in a Mn1Co5Ox solid solution catalyst. Furthermore, the introduction of a Mn dopant contributed to the durability of Mn1Co5Ox in acidic OER, thereby exhibiting outstanding catalytic stability for nearly 300 hours at 100 mA cm−2 current density. In addition, DFT studies provided insight into how Mn1Co5Ox enhances the catalytic performance of the OER. In conclusion, this study offers valuable insight into designing efficient OER catalysts using MnCoOx solid solutions as a promising candidate. [ABSTRACT FROM AUTHOR]

Engineering efficient catalyst interfaces offers a constructive way to boost activity and stability in the field of water electrolysis. Here, unique core–shell FeCoS@CoMoP heterostructure nanoparticles are rationally fabricated on a porous Ni foam through hydrothermal and electrodeposition methods. The as-prepared electrocatalyst exhibits efficient pH-universal hydrogen evolution reaction (HER) activity along with a satisfactory alkaline oxygen evolution reaction (OER) performance, extremely small overpotentials, and Tafel values, achieving prominent durability and stability. A series of structural characterizations help identify the reactive centers during the catalytic procedure and the tight interfacial interaction between the shell and core materials. Density functional theory (DFT) calculations reveal that the surface electrodeposition of CoMoP not only tunes the d-band center but also obviously decreases the Gibbs free energies in the HER/OER processes. It can be expected that the three-dimensional self-supported catalytic system will hold strong promise for effective water splitting, energy storage, and energy transformation devices. [ABSTRACT FROM AUTHOR]

Two-dimensional transition-metal carbides and nitrides (MXenes) show great potential in aerogel flexible piezoresistive sensors owing to their versatile surface chemistry, high carrier mobility, outstanding metallic conductivity, and adjustable interlayer spacing under applied stress. However, the pure MXene aerogel exhibits significant plastic deformation or brittle mechanical performance due to the weak interactions between the nanosheets. Herein, a series of MXene/polyimide/silver nanowire composite aerogels with aligned lamellar microstructure are fabricated by bidirectional freezing and annealing strategies. The introduction of polyimide (PI) and silver nanowires (AgNWs) significantly improves the mechanical properties of the MXene-based aerogel. The obtained lightweight composite aerogel shows superelasticity with large reversible compressibility, excellent stability, and outstanding fatigue resistance. Moreover, owing to the highly aligned lamellar microstructure of the composite aerogel and the excellent conductivity of MXene and AgNWs, the composite aerogel exhibits great sensing performance with high sensitivity (gauge factor ∼27.8) and ultralow detection limit (<0.6 Pa). Based on the MXene/PI/AgNW composite aerogels, a series of wearable sensor applications are demonstrated. [ABSTRACT FROM AUTHOR]

Shuttle effect and sluggish redox kinetics of sulfur species still hinder the practical application of lithium‐sulfur batteries (LSBs). Herein, a strategy of integrating sub‐nano catalysts into metal‐organic framework (MOF) is proposed for developing efficient sulfur host to tackle these issues. The designed MOF host (MOF‐TOC) endowed with sub‐nano TiO clusters (TOCs) in the mesopores of MOF can act as an efficient reaction chamber in LSBs. Systematic electrochemical measurements and calculations demonstrate that MOF‐TOC can trap and confine lithium polysulfides (LiPSs) via strong chemical interaction. Moreover, the highly active TOCs isolated in different nanopores can accelerate the bidirectional redox reaction of sulfur species through the d‐p orbital hybridization with sulfur species. Benefiting from these merits, MOF‐TOC delivers LSBs with remarkably improved areal capacity and cycling stability at high sulfur loadings and lean electrolytes. This work gives insight into the rational design of catalyst‐containing MOF hosts and will shed light on the development of advanced catalytic hosts for high‐performance LSBs. [ABSTRACT FROM AUTHOR]

Timely separation of products from the reactant is a great challenge for a catalytic reaction process. In this study, we fabricated a novel poly(vinylidene fluoride) composite membrane with noble metal (Au, Ag, and Pd) nanoparticles in membrane pores to solve the faced challenge. The composite membrane has a unique structure comprising membrane surfaces with only PVDF and membrane pores with poly(methacrylic acid) microspheres coated by noble metal nanoparticles. The composite membrane is used for the catalytic reduction of p-nitrophenol and the results indicate that the catalytic reaction can rapidly proceed. What is more, the product formed in reaction process can be immediately isolated from the reactant. Other drawbacks such as the easy aggregation and the difficult separation generally encountered by the metal nanocatalysts are also avoided by using the composite membrane. In operation process, the composite membrane shows good thermal, mechanical and catalytic stability. These attracted merits make the prepared composite membrane have desirable prospects in catalytic application., INTRODUCTION Noble metal nanoparticles (NMNPs) have excellent catalytic reactivity due to their high surface area-to-volume ratios and excellent surface properties [1, 2]. However, their surfaces are often covered due to [...]

Thermoelectric (TE) materials allow us to harvest energy practically from any heat source, including heat that would be otherwise wasted. This huge promise of energy harvesting is contingent on identifying/designing materials having higher efficiency than presently available ones. However, due to the vastness of the chemical space of materials, only a small fraction of potential candidates has been experimentally and/or computationally scanned thus far. By employing an artificial intelligence (AI) approach based on compressed-sensing symbolic regression analysis of experimental data in an active-learning framework, we have not only identified a trend in the materials composition for superior TE performance, but also predicted and experimentally synthesized several high-performing TE chalcogenides. In particular, p-type Cu0.45Ag0.55GaTe2 shows a very high experimental figure of merit (zT) ∼1.90 at 770 K using experimentally measured heat capacity (Cp). The present work demonstrates not only experimental realization of AI-predicted high-zT TE, but also the importance and potential of physically informed descriptors in material science, particularly for relatively small but well-controlled datasets typically available from experiments. [ABSTRACT FROM AUTHOR]

Catalysts for chemoselective hydrogenation are of vital importance for the synthesis of various important chemicals and intermediates. Herein we developed a simple method for preparing a highly efficient Ni-MoCx nanocomposite catalyst via temperature-programmed carburization of a polyoxometalate precursor. X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) analyses indicate that the resulting mesoporous nanocomposite catalyst is made up of well-dispersed metallic nickel particles embedded in a MoCx matrix. This catalyst exhibits high activity and selectivity (> 99%) in the hydrogenation of various substituted nitroaromatics to corresponding anilines. The high efficiency is attributed to the intimate contact of the constituents favoring electron transfer and hydrogen adsorption. Dihydrogen is physisorbed on the carbide support and dissociates on the nickel particles, as evidenced by Mo K-edge X-ray absorption near-edge structure (XANES) spectra, density functional theory (DFT), and hydrogen—deuterium exchange. The remarkable catalytic performance of the catalyst could be traced back to the synergistic interaction between the Ni particles and the carbide support. In-situ infrared spectroscopy and DFT simulations indicated that the adsorption/activation of the nitro group is favored compared to that of other substituents at the aromatic ring. In recyclability tests, the Ni-MoCx nanocomposite showed no significant loss of catalytic performance in seven consecutive runs, indicating its robust nature. [ABSTRACT FROM AUTHOR]