Single-Atom Alloy Formation via Reaction-Driven Catalyst Restructuring.

We demonstrate that single-atom alloy catalysts can be made by exposing physical mixtures of monometallic supported Cu and Pd catalysts to vinyl acetate (VA) synthesis reaction conditions. This reaction induces the formation of mobile clusters of metal diacetate species that drive extensive metal nanoparticle restructuring, leading to atomic dispersion of the precious metal, smaller nanoparticle sizes than the parent catalysts, and high activity and selectivity for both VA synthesis and ethanol dehydrogenation reactions. This approach is scalable and appears to be generalizable to other alloy catalysts.

Multivariate Bayesian Optimization of CoO Nanoparticles for CO Hydrogenation Catalysis.

The hydrogenation of CO holds promise for transforming the production of renewable fuels and chemicals. However, the challenge lies in developing robust and selective catalysts for this process. Transition metal oxide catalysts, particularly cobalt oxide, have shown potential for CO hydrogenation, with performance heavily reliant on crystal phase and morphology.

Molecular Precursor Approach to Sulfur-Free CuInSe: Replacing Thiol Coordination in Soluble Metal Complexes.

Solution-processed CuInSe films have generally relied on sulfide or sulfoselenide precursor films that, during the grain growth process, hamper the growth of thicker films and lead to the formation of a fine-grain layer. However, recent research has indicated that sulfur reduction in the precursor film modifies the grain growth mechanism and may enable the fabrication of thicker absorbers that are free of any fine-grain layer. In this work, we pursue direct solution deposition of sulfur-free CuInSe films from the molecular precursor approach.

A high-performance hydroxide exchange membrane enabled by Cu-crosslinked chitosan.

Ion exchange membranes are widely used to selectively transport ions in various electrochemical devices. Hydroxide exchange membranes (HEMs) are promising to couple with lower cost platinum-free electrocatalysts used in alkaline conditions, but are not stable enough in strong alkaline solutions. Herein, we present a Cu-crosslinked chitosan (chitosan-Cu) material as a stable and high-performance HEM.

Reactivity of (bi-Oxazoline)organonickel Complexes and Revision of a Catalytic Mechanism.

Bi-Oxazoline (biOx) has emerged as an effective ligand framework for promoting nickel-catalyzed cross-coupling, cross-electrophile coupling, and photoredox-nickel dual catalytic reactions. This report fills the knowledge gap of the organometallic reactivity of (biOx)Ni complexes, including catalyst reduction, oxidative electrophile activation, radical capture, and reductive elimination. The biOx ligand displays no redox activity in (biOx)Ni(I) complexes, in contrast to other chelating imine and oxazoline ligands.

Olefin oligomerization by main group Ga and Zn single site catalysts on SiO.

In heterogeneous catalysis, olefin oligomerization is typically performed on immobilized transition metal ions, such as Ni and Cr. Here we report that silica-supported, single site catalysts containing immobilized, main group Zn and Ga ion sites catalyze ethylene and propylene oligomerization to an equilibrium distribution of linear olefins with rates similar to that of Ni. The molecular weight distribution of products formed on Zn is similar to Ni, while Ga forms higher molecular weight olefins.

High-Capacitance Pseudocapacitors from Li Ion Intercalation in Nonporous, Electrically Conductive 2D Coordination Polymers.

Electrochemical capacitors (ECs) have emerged as reliable and fast-charging electrochemical energy storage devices that offer high power densities. Their use is still limited, nevertheless, by their relatively low energy density. Because high specific surface area and electrical conductivity are widely seen as key metrics for improving the energy density and overall performance of ECs, materials that have excellent electrical conductivities but are otherwise nonporous, such as coordination polymers (CPs), are often overlooked.

Atomically precise single-crystal structures of electrically conducting 2D metal-organic frameworks.

Electrically conducting 2D metal-organic frameworks (MOFs) have attracted considerable interest, as their hexagonal 2D lattices mimic graphite and other 2D van der Waals stacked materials. However, understanding their intrinsic properties remains a challenge because their crystals are too small or of too poor quality for crystal structure determination. Here, we report atomically precise structures of a family of 2D π-conjugated MOFs derived from large single crystals of sizes up to 200 μm, allowing atomic-resolution analysis by a battery of high-resolution diffraction techniques.

Electrocatalytic CO Reduction over CuP Nanoparticles Generated via a Molecular Precursor Route.

The design of nanoparticles (NPs) with tailored morphologies and finely tuned electronic and physical properties has become a key strategy for controlling selectivity and improving conversion efficiency in a variety of important electrocatalytic transformations. Transition metal phosphide NPs, in particular, have emerged as a versatile class of catalytic materials due to their multifunctional active sites and composition- and phase-dependent properties. Access to targeted transition metal phosphide NPs with controlled features is necessary to tune the catalytic activity.

A pyridinic Fe-N macrocycle models the active sites in Fe/N-doped carbon electrocatalysts.

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum catalysts for the oxygen reduction reaction (ORR) in fuel cells; however, their active site structures remain poorly understood. A leading postulate is that the iron-containing active sites exist primarily in a pyridinic Fe-N ligation environment, yet, molecular model catalysts generally feature pyrrolic coordination. Herein, we report a molecular pyridinic hexaazacyclophane macrocycle, (phenN)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for ORR to a typical Fe-N-C material and prototypical pyrrolic iron macrocycles.

Continuous Electrical Conductivity Variation in M(Hexaiminotriphenylene) (M = Co, Ni, Cu) MOF Alloys.

We report on the continuous fine-scale tuning of band gaps over 0.4 eV and of the electrical conductivity of over 4 orders of magnitude in a series of highly crystalline binary alloys of two-dimensional electrically conducting metal-organic frameworks M(HITP) (M = Co, Ni, Cu; HITP = 2,3,6,7,10,11-hexaiminotriphenylene). The isostructurality in the M(HITP) series permits the direct synthesis of binary alloys (MM')(HITP) (MM' = CuNi, CoNi, and CoCu) with metal compositions precisely controlled by precursor ratios.

Analyzing and Tuning the Chalcogen-Amine-Thiol Complexes for Tailoring of Chalcogenide Syntheses.

The amine-thiol solvent system has been used extensively to synthesize metal chalcogenide thin films and nanoparticles because of its ability to dissolve various metal and chalcogen precursors. While previous studies of this solvent system have focused on understanding the dissolution of metal precursors, here we provide an in-depth investigation of the dissolution of chalcogens, specifically Se and Te. Analytical techniques, including Raman, X-ray absorption, and NMR spectroscopy and high-resolution tandem mass spectrometry, were used to identify pathways for Se and Te dissolution in butylamine-ethanethiol and ethylenediamine-ethanethiol solutions.

Ensemble Effect in Bimetallic Electrocatalysts for CO Reduction.

Alloying is an important strategy for the design of catalytic materials beyond pure metals. The conventional alloy catalysts however lack precise control over the local atomic structures of active sites. Here we report on an investigation of the active-site ensemble effect in bimetallic Pd-Au electrocatalysts for CO reduction.