Pt@UiO-66 Heterostructures for Highly Selective Detection of Hydrogen Peroxide with an Extended Linear Range

In this study, a good core–shell heterostructure of Pt NPs@UiO-66 was fabricated by encapsulating presynthesized platinum nanoparticles (Pt NPs) into the host matrix of UiO-66 which possesses the slender triangular windows with a diameter of 6 Å. The transmission electron microscopy images exhibited that the number of the encapsulated Pt NPs and the crystalline morphology of as-synthesized core–shell heterostructure samples had a series of changes with increasing the volume of the injected Pt NPs precursor solution. Among these samples, the Pt NPs@UiO-66-2 sample had a good crystalline morphology with several well-dispersed Pt NPs encapsulated in UiO-66 frameworks. But there were no obvious Pt NPs observed in the Pt NPs@UiO-66-1 sample, and for the Pt NPs@UiO-66-3 sample, the number of Pt NPs encapsulated in UiO-66 matrix notably reduced and the metal organic framework (MOF) crystals became small and aggregated. The electrochemical measurements showed that the Pt NPs@UiO-66-2 sample modified glass carbon electrode (GCE) presented a remarkable electrocatalytic activity toward hydrogen peroxide (H₂O₂) oxidation, including an excellent anti-interference performance even if the concentration of the interference species was the same as the H₂O₂, an extended linear range from 5 μM to 14.75 mM, a low detection limit, as well as good stability and reproducibility. The results indicate the superiority of MOFs in H₂O₂ detection. And more importantly, it will provide a new opportunity to promote the anti-interference performance of the nonenzyme electrochemical sensors

Hybrids of Cobalt/Iron Phosphides Derived from Bimetal–Organic Frameworks as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction

The electrochemical splitting of water, as an efficient and large-scale method to produce H₂, is still hindered by the sluggish kinetics of the oxygen evolution reaction (OER) at the anode. Considering the synergetic effect of the different metal sites with coordination on the surface of electrocatalysts, the hybrids of Co/Fe phosphides (denoted as Co-Fe-P) is prepared by one-step phosphorization of CoFe metal–organic frameworks for the first time as highly efficient electrocatalysts for OER. Benefiting from the synergistic effect of Co and Fe, the high valence of Co ions induced by strongly electronegative P and N and the large electrochemical active surface area (ECSA) originated from exposed nanowires on the surface of Co/Fe phosphides, the resultant Co-Fe-P-1.7 exhibits remarkable electrocatalytic performances for OER in 1.0 M KOH, affording an overpotential as low as 244 mV at a current density of 10 mA/cm², a small Tafel slope of 58 mV/dec, and good stability, which is superior to that of the state-of-the-art OER electrocatalysts. In addition, the two-electrode cell with Co-Fe-P-1.7 modified Ni foam as anode and cathode in an alkaline electrolyte, respectively, exhibits the decomposition potential of ca. 1.60 V at a current density of 10 mA/cm² and excellent stability

Ni/CdS Bifunctional Ti@TiO₂ Core–Shell Nanowire Electrode for High-Performance Nonenzymatic Glucose Sensing

In this work, a Ni/CdS bifunctional Ti@TiO₂ core–shell nanowire electrode with excellent electrochemical sensing property was successfully constructed through a hydrothermal and electrodeposition method. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to confirm the synthesis and characterize the morphology of the as-prepared samples. The results revealed that the CdS layer between Ni and TiO₂ plays an important role in the uniform nucleation and the following growth of highly dispersive Ni nanoparticle on the Ti@TiO₂ core–shell nanowire surface. The bifunctional nanostructured electrode was applied to construct an electrochemical nonenzymatic sensor for the reliable detection of glucose. Under optimized conditions, this nonenzymatic glucose sensor displayed a high sensitivity up to 1136.67 μA mM^–1 cm^–2, a wider liner range of 0.005–12 mM, and a lower detection limit of 0.35 μM for glucose oxidation. The high dispersity of Ni nanoparticles, combined with the anti-poisoning faculty against the intermediate derived from the self-cleaning ability of CdS under the photoexcitation, was considered to be responsible for these enhanced electrochemical performances. Importantly, favorable reproducibility and long-term performance were also obtained thanks to the robust frameworks. All these results indicate this novel electrode is a promising candidate for nonenzymatic glucose sensing

Ti@TiO₂ Nanowire Electrode with Polydisperse Gold Nanoparticles for Electrogenerated Chemiluminescence and Surface Enhanced Raman Spectroelectrochemistry

We present a multifunctional nanostructured electrode with Ti core and TiO₂ shell (Ti@TiO₂) nanowires (NWs) decorated with Au nanoparticles (NP) for studying spectroelectrochemistry (e.g., electrogenerated chemiluminescence, ECL) and surface enhanced Raman scattering (SERS). The so-called N3 dye (<i>cis</i>-[Ru (4,4′-COOH-2,2′-bpy)₂(NCS)₂]) is used as probe molecule for studying ECL and SERS enhancement capability of this nanostructured electrode. The SERS enhancement of N3 dye is determined by surface coverage and particle size of Au NPs and the surface self-assembly configuration of N3 on this new nanostructured electrode. ECL and in-situ SERS spectroelectrochemistry studies suggest that Au NP decorated Ti@TiO₂ NW electrode can serve as a new spectroelectrochemistry platform for helping understand redox reaction mechanism and quantitative analysis with the combined methods of optical spectroscopy and electrochemistry

Highly Conductive Nanostructured C-TiO₂ Electrodes with Enhanced Electrochemical Stability and Double Layer Charge Storage Capacitance

The present work reports the structural and electrochemical properties of carbon-modified nanostructured TiO₂ electrodes (C-TiO₂) prepared by anodizing titanium in a fluoride-based electrolyte followed by thermal annealing in an atmosphere of methane and hydrogen in the presence of Fe precursors. The C-TiO₂ nanostructured electrodes are highly conductive and contain more than 1 × 10¹⁰ /cm² of nanowires or nanotubes to enhance their double layer charge capacitance and electrochemical stability. Electrogenerated chemiluminescence (ECL) study shows that a C-TiO₂ electrode can replace noble metal electrodes for ultrasensitive ECL detection. Dynamic potential control experiments of redox reactions show that the C-TiO₂ electrode has a broad potential window for a redox reaction. Double layer charging capacitance of the C-TiO₂ electrode is found to be 3 orders of magnitude higher than an ideal planar electrode because of its high surface area and efficient charge collection capability from the nanowire structured surface. The effect of anodization voltage, surface treatment with Fe precursors for carbon modification, the barrier layer between the Ti substrate, and anodized layer on the double layer charging capacitance is studied. Ferrocene carboxylic acid binds covalently to the anodized Ti surface forming a self-assembled monolayer, serving as an ideal precursor layer to yield C-TiO₂ electrodes with better double layer charging performance than the other precursors

Powerful Orbital Hybridization of Copper–Silver Bimetallic Nanosheets for Electrocatalytic Nitrogen Reduction to Ammonia

Electrochemical nitrogen reduction (eNRR) is a promising strategy to replace the energy- and capital-intensive Haber–Bosch process. Unfortunately, the low selectivity of the eNRR process impedes the industrial application of this approach. In this work, a highly efficient and stable NRR electrocatalyst is obtained via coreduction of Cu and Ag precursors using the holly leaves as reducing agents. The as-obtained Cu3Ag bimetallic nanosheets exhibit excellent NRR performance with an NH3 production rate of 31.3 μg h–1 mg–1cat. and a Faradaic efficiency of 31.3% at −0.2 V vs RHE. According to density functional theory (DFT) calculation, the outstanding performance of Cu3Ag bimetallic nanosheets could be caused by the fact that Ag optimizes the 3d orbital occupation of Cu and synergistically enhances the charge transfer during the NRR process, resulting in a suitable adsorption strength of the intermediates

Ru-Doped Ultrasmall Cu Nanoparticles Decorated with Carbon for Electroreduction of Nitrate to Ammonia

Electrocatalytic nitrate reduction reaction offers a sustainable approach to treating wastewater and synthesizing high-value ammonia under ambient conditions. However, electrocatalysts with low faradaic efficiency and selectivity severely hinder the development of nitrate-to-ammonia conversion. Herein, Ru-doped ultrasmall copper nanoparticles loaded on a carbon substrate (Cu–Ru@C) were fabricated by the pyrolysis of Cu-BTC metal–organic frameworks (MOFs). The Cu–[email protected] catalyst exhibits a high faradaic efficiency (FE) of 90.4% at −0.6 V (vs RHE) and an ammonia yield rate of 1700.36 μg h–1mgcat.–1 at −0.9 V (vs RHE). Moreover, the nitrate conversion rate is almost 100% over varied pHs (including acid, neutral, and alkaline electrolytes) and different nitrate concentrations. The remarkable performance is attributed to the synergistic effect between Cu and Ru and the excellent conductivity of the carbon substrate. This work will open an exciting avenue to exploring MOF derivatives for ambient ammonia synthesis via selective electrocatalytic nitrate reduction

Multifunctional Ln–MOF Luminescent Probe for Efficient Sensing of Fe³⁺, Ce³⁺, and Acetone

A new series of five three-dimensional Ln­(III) metal–organic frameworks (MOFs) formulated as [Ln₄(μ₆-L)₂(μ-HCOO)­(μ₃-OH)₃(μ₃-O)­(DMF)₂(H₂O)₄]_<i>n</i> {Ln³⁺ = Tb³⁺ (<b>1</b>), Eu³⁺ (<b>2</b>), Gd³⁺ (<b>3</b>), Dy³⁺ (<b>4</b>), and Er³⁺ (<b>5</b>)} was successfully obtained via a solvothermal reaction between the corresponding lanthanide­(III) nitrates and 2-(6-carboxypyridin-3-yl)­terephthalic acid (H₃L). All of the obtained compounds were fully characterized, and their structures were established by single-crystal X-ray diffraction. All products are isostructural and possess porous 3D networks of the fluorite topological type, which are driven by the cubane-like [Ln₄(μ₃–OH)₃(μ₃-O)­(μ-HCOO)]⁶⁺ blocks and μ₆-L^3– spacers. Luminescent and sensing properties of <b>1</b>–<b>5</b> were investigated in detail, revealing a unique capability of Tb–MOF (<b>1</b>) for sensing acetone and metal­(III) cations (Fe³⁺ or Ce³⁺) with high efficiency and selectivity. Apart from a facile recyclability after sensing experiments, the obtained Tb–MOF material features a remarkable stability in a diversity of environments such as common solvents, aqueous solutions of metal ions, and solutions with a broad pH range from 4 to 11. In addition, compound <b>1</b> represents a very rare example of the versatile Ln–MOF probe capable of sensing Ce³⁺ or Fe³⁺ cations or acetone molecules

Multifunctional Ln–MOF Luminescent Probe for Efficient Sensing of Fe³⁺, Ce³⁺, and Acetone

A new series of five three-dimensional Ln­(III) metal–organic frameworks (MOFs) formulated as [Ln₄(μ₆-L)₂(μ-HCOO)­(μ₃-OH)₃(μ₃-O)­(DMF)₂(H₂O)₄]_<i>n</i> {Ln³⁺ = Tb³⁺ (<b>1</b>), Eu³⁺ (<b>2</b>), Gd³⁺ (<b>3</b>), Dy³⁺ (<b>4</b>), and Er³⁺ (<b>5</b>)} was successfully obtained via a solvothermal reaction between the corresponding lanthanide­(III) nitrates and 2-(6-carboxypyridin-3-yl)­terephthalic acid (H₃L). All of the obtained compounds were fully characterized, and their structures were established by single-crystal X-ray diffraction. All products are isostructural and possess porous 3D networks of the fluorite topological type, which are driven by the cubane-like [Ln₄(μ₃–OH)₃(μ₃-O)­(μ-HCOO)]⁶⁺ blocks and μ₆-L^3– spacers. Luminescent and sensing properties of <b>1</b>–<b>5</b> were investigated in detail, revealing a unique capability of Tb–MOF (<b>1</b>) for sensing acetone and metal­(III) cations (Fe³⁺ or Ce³⁺) with high efficiency and selectivity. Apart from a facile recyclability after sensing experiments, the obtained Tb–MOF material features a remarkable stability in a diversity of environments such as common solvents, aqueous solutions of metal ions, and solutions with a broad pH range from 4 to 11. In addition, compound <b>1</b> represents a very rare example of the versatile Ln–MOF probe capable of sensing Ce³⁺ or Fe³⁺ cations or acetone molecules