Enriching Reaction Intermediates in Multishell Structured Copper Catalysts for Boosted Propanol Electrosynthesis from Carbon Monoxide

Fine-tuned catalysts that alter the diffusion kinetics of reaction intermediates is of great importance for achieving high-performance multicarbon (C2+) product generation in carbon monoxide (CO) reduction. Herein, we conduct a structural design based on Cu2O nanoparticles and present an effective strategy for enhancing propanol electrosynthesis from CO. The electrochemical characterization, operando Raman monitoring, and finite-element method simulations reveal that the multishell structured catalyst can realize the enrichment of C1 and C2 intermediates by nanoconfinement space, leading to the possibility of further coupling. Consequently, the multishell copper catalyst realizes a high Faraday efficiency of 22.22 ± 0.38% toward propanol at the current density of 50 mA cm–2

Monodisperse MPt (M = Fe, Co, Ni, Cu, Zn) Nanoparticles Prepared from a Facile Oleylamine Reduction of Metal Salts

We report a simple, yet general, approach to monodisperse MPt (M = Fe, Co, Ni, Cu, Zn) nanoparticles (NPs) by coreduction of M­(acac)₂ and Pt­(acac)₂ (acac = acetylacetonate) with oleylamine at 300 °C. In the current reaction condition, oleylamine serves as the reducing agent, surfactant, and solvent. As an example, we describe in details the synthesis of 9.5 nm CoPt NPs with their compositions controlled from Co₃₇Pt₆₃ to Co₆₉Pt₃₁. These NPs show composition-dependent structural and magnetic properties. The unique oleylamine reduction process makes it possible to prepare MPt NPs with their physical properties and surface chemistry better rationalized for magnetic or catalytic applications

Active and Selective Conversion of CO₂ to CO on Ultrathin Au Nanowires

In this communication, we show that ultrathin Au nanowires (NWs) with dominant edge sites on their surface are active and selective for electrochemical reduction of CO₂ to CO. We first develop a facile seed-mediated growth method to synthesize these ultrathin (2 nm wide) Au NWs in high yield (95%) by reducing HAuCl₄ in the presence of 2 nm Au nanoparticles (NPs). These NWs catalyze CO₂ reduction to CO in aqueous 0.5 M KHCO₃ at an onset potential of −0.2 V (vs reversible hydrogen electrode). At −0.35 V, the reduction Faradaic efficiency (FE) reaches 94% (mass activity 1.84 A/g Au) and stays at this level for 6 h without any noticeable activity change. Density functional theory (DFT) calculations suggest that the excellent catalytic performance of these Au NWs is attributed both to their high mass density of reactive edge sites (≥16%) and to the weak CO binding on these sites. These ultrathin Au NWs are the most efficient nanocatalyst ever reported for electrochemical reduction of CO₂ to CO

New Approach to Fully Ordered fct-FePt Nanoparticles for Much Enhanced Electrocatalysis in Acid

Fully ordered face-centered tetragonal (fct) FePt nanoparticles (NPs) are synthesized by thermal annealing of the MgO-coated dumbbell-like FePt-Fe₃O₄ NPs followed by acid washing to remove MgO. These fct-FePt NPs show strong ferromagnetism with room temperature coercivity reaching 33 kOe. They serve as a robust electrocatalyst for the oxygen reduction reaction (ORR) in 0.1 M HClO₄ and hydrogen evolution reaction (HER) in 0.5 M H₂SO₄ with much enhanced activity (the most active fct-structured alloy NP catalyst ever reported) and stability (no obvious Fe loss and NP degradation after 20 000 cycles between 0.6 and 1.0 V (vs RHE)). Our work demonstrates a reliable approach to FePt NPs with much improved fct-ordering and catalytic efficiency for ORR and HER

Tuning Sn-Catalysis for Electrochemical Reduction of CO₂ to CO via the Core/Shell Cu/SnO₂ Structure

Tin (Sn) is known to be a good catalyst for electrochemical reduction of CO₂ to formate in 0.5 M KHCO₃. But when a thin layer of SnO₂ is coated over Cu nanoparticles, the reduction becomes Sn-thickness dependent: the thicker (1.8 nm) shell shows Sn-like activity to generate formate whereas the thinner (0.8 nm) shell is selective to the formation of CO with the conversion Faradaic efficiency (FE) reaching 93% at −0.7 V (vs reversible hydrogen electrode (RHE)). Theoretical calculations suggest that the 0.8 nm SnO₂ shell likely alloys with trace of Cu, causing the SnO₂ lattice to be uniaxially compressed and favors the production of CO over formate. The report demonstrates a new strategy to tune NP catalyst selectivity for the electrochemical reduction of CO₂ via the tunable core/shell structure

Monodisperse Au Nanoparticles for Selective Electrocatalytic Reduction of CO₂ to CO

We report selective electrocatalytic reduction of carbon dioxide to carbon monoxide on gold nanoparticles (NPs) in 0.5 M KHCO₃ at 25 °C. Among monodisperse 4, 6, 8, and 10 nm NPs tested, the 8 nm Au NPs show the maximum Faradaic efficiency (FE) (up to 90% at −0.67 V vs reversible hydrogen electrode, RHE). Density functional theory calculations suggest that more edge sites (active for CO evolution) than corner sites (active for the competitive H₂ evolution reaction) on the Au NP surface facilitates the stabilization of the reduction intermediates, such as COOH*, and the formation of CO. This mechanism is further supported by the fact that Au NPs embedded in a matrix of butyl-3-methyl­imid­azolium hexafluorophosphate for more efficient COOH* stabilization exhibit even higher reaction activity (3 A/g mass activity) and selectivity (97% FE) at −0.52 V (vs RHE). The work demonstrates the great potentials of using monodisperse Au NPs to optimize the available reaction intermediate binding sites for efficient and selective electrocatalytic reduction of CO₂ to CO

Self-Illuminating ⁶⁴Cu-Doped CdSe/ZnS Nanocrystals for in Vivo Tumor Imaging

Construction of self-illuminating semiconducting nanocrystals, also called quantum dots (QDs), has attracted much attention recently due to their potential as highly sensitive optical probes for biological imaging applications. Here we prepared a self-illuminating QD system by doping positron-emitting radionuclide ⁶⁴Cu into CdSe/ZnS core/shell QDs via a cation-exchange reaction. The ⁶⁴Cu-doped CdSe/ZnS QDs exhibit efficient Cerenkov resonance energy transfer (CRET). The signal of ⁶⁴Cu can accurately reflect the biodistribution of the QDs during circulation with no dissociation of ⁶⁴Cu from the nanoparticles. We also explored this system for in vivo tumor imaging. This nanoprobe showed high tumor-targeting ability in a U87MG glioblastoma xenograft model (12.7% ID/g at 17 h time point) and feasibility for in vivo luminescence imaging of tumor in the absence of excitation light. The availability of these self-illuminating integrated QDs provides an accurate and convenient tool for in vivo tumor imaging and detection

A New Core/Shell NiAu/Au Nanoparticle Catalyst with Pt-like Activity for Hydrogen Evolution Reaction

We report a general approach to NiAu alloy nanoparticles (NPs) by co-reduction of Ni­(acac)₂ (acac = acetylacetonate) and HAuCl₄·3H₂O at 220 °C in the presence of oleylamine and oleic acid. Subject to potential cycling between 0.6 and 1.0 V (vs reversible hydrogen electrode) in 0.5 M H₂SO₄, the NiAu NPs are transformed into core/shell NiAu/Au NPs that show much enhanced catalysis for hydrogen evolution reaction (HER) with Pt-like activity and much robust durability. The first-principles calculations suggest that the high activity arises from the formation of Au sites with low coordination numbers around the shell. Our synthesis is not limited to NiAu but can be extended to FeAu and CoAu as well, providing a general approach to MAu/Au NPs as a class of new catalyst superior to Pt for water splitting and hydrogen generation

Chelator-Free ⁶⁴Cu-Integrated Gold Nanomaterials for Positron Emission Tomography Imaging Guided Photothermal Cancer Therapy

Using positron emission tomography (PET) imaging to monitor and quantitatively analyze the delivery and localization of Au nanomaterials (NMs), a widely used photothermal agent, is essential to optimize therapeutic protocols to achieve individualized medicine and avoid side effects. Coupling radiometals to Au NMs <i>via</i> a chelator faces the challenges of possible detachment of the radiometals as well as surface property changes of the NMs. In this study, we reported a simple and general chelator-free ⁶⁴Cu radiolabeling method by chemically reducing ⁶⁴Cu on the surface of polyethylene glycol (PEG)-stabilized Au NMs regardless of their shape and size. Our ⁶⁴Cu-integrated NMs are proved to be radiochemically stable and can provide an accurate and sensitive localization of NMs through noninvasive PET imaging. We further integrated ⁶⁴Cu onto arginine-glycine-aspartic acid (RGD) peptide modified Au nanorods (NRs) for tumor theranostic application. These NRs showed high tumor targeting ability in a U87MG glioblastoma xenograft model and were successfully used for PET image-guided photothermal therapy