A Ce-CuZn catalyst with abundant Cu/Zn-OV-Ce active sites for CO2 hydrogenation to methanol.

CO2 hydrogenation to chemicals and fuels is a significant approach for achieving carbon neutrality. It is essential to rationally design the chemical structure and catalytic active sites towards the development of efficient catalysts. Here we show a Ce-CuZn catalyst with enriched Cu/Zn-OV-Ce active sites fabricated through the atomic-level substitution of Cu and Zn into Ce-MOF precursor. The Ce-CuZn catalyst exhibits a high methanol selectivity of 71.1% and a space-time yield of methanol up to 400.3 g·kgcat-1·h-1 with excellent stability for 170 h at 260 °C, comparable to that of the state-of-the-art CuZnAl catalysts. Controlled experiments and DFT calculations confirm that the incorporation of Cu and Zn into CeO2 with abundant oxygen vacancies can facilitate H2 dissociation energetically and thus improve CO2 hydrogenation over the Ce-CuZn catalyst via formate intermediates. This work offers an atomic-level design strategy for constructing efficient multi-metal catalysts for methanol synthesis through precise control of active sites.

Reactant enrichment in hollow void of Pt NPs@MnOx nanoreactors for boosting hydrogenation performance.

In confined mesoscopic spaces, the unraveling of a catalytic mechanism with complex mass transfer and adsorption processes such as reactant enrichment is a great challenge. In this study, a hollow nanoarchitecture of MnOx-encapsulated Pt nanoparticles was designed as a nanoreactor to investigate the reactant enrichment in a mesoscopic hollow void. By employing advanced characterization techniques, we found that the reactant-enrichment behavior is derived from directional diffusion of the reactant driven through the local concentration gradient and this increased the amount of reactant. Combining experimental results with density functional theory calculations, the superior cinnamyl alcohol (COL) selectivity originates from the selective adsorption of cinnamaldehyde (CAL) and the rapid formation and desorption of COL in the MnOx shell. The superb performance of 95% CAL conversion and 95% COL selectivity is obtained at only 0.5 MPa H2 and 40 min. Our findings showcase that a rationally designed nanoreactor could boost catalytic performance in chemoselective hydrogenation, which can be of great aid and potential in various application scenarios.

Design of Hollow Nanoreactors for Size- and Shape-Selective Catalytic Semihydrogenation Driven by Molecular Recognition.

Mimicking the structures and functions of cells to create artificial organelles has spurred the development of efficient strategies for production of hollow nanoreactors with biomimetic catalytic functions. However, such structure are challenging to fabricate and are thus rarely reported. We report the design of hollow nanoreactors with hollow multishelled structure (HoMS) and spatially loaded metal nanoparticles. Starting from a molecular-level design strategy, well-defined hollow multishelled structure phenolic resins (HoMS-PR) and carbon (HoMS-C) submicron particles were accurately constructed. HoMS-C serves as an excellent, versatile platform, owing to its tunable properties with tailored functional sites for achieving precise spatial location of metal nanoparticles, internally encapsulated (Pd@HoMS-C) or externally supported (Pd/HoMS-C). Impressively, the combination of the delicate nanoarchitecture and spatially loaded metal nanoparticles endow the pair of nanoreactors with size-shape-selective molecular recognition properties in catalytic semihydrogenation, including high activity and selectivity of Pd@HoMS-C for small aliphatic substrates and Pd/HoMS-C for large aromatic substrates. Theoretical calculations provide insight into the pair of nanoreactors with distinct behaviors due to the differences in energy barrier of substrate adsorption. This work provides guidance on the rational design and accurate construction of hollow nanoreactors with precisely located active sites and a finely modulated microenvironment by mimicking the functions of cells.

Diagnosing and Correcting the Failure of the Solid-State Polymer Electrolyte for Enhancing Solid-State Lithium-Sulfur Batteries.

Solid-state polymer electrolytes (SPEs) attract great interest in developing high-performance yet reliable solid-state batteries. However, understanding of the failure mechanism of the SPE and SPE-based solid-state batteries remains in its infancy, posing a great barrier to practical solid-state batteries. Herein, the high accumulation and clogging of "dead" lithium polysulfides (LiPS) on the interface between the cathode and SPE with intrinsic diffusion limitation is identified as a critical failure cause of SPE-based solid-state Li-S batteries. It induces a poorly reversible chemical environment with retarded kinetics on the cathode-SPE interface and in bulk SPEs, starving the Li-S redox in solid-state cells. This observation is different from the case in liquid electrolytes with free solvent and charge carriers, where LiPS dissolve but remain alive for electrochemical/chemical redox without interfacial clogging. Electrocatalysis demonstrates the feasibility of tailoring the chemical environment in diffusion-restricted reaction media for reducing Li-S redox failure in the SPE. It enables Ah-level solid-state Li-S pouch cells with a high specific energy of 343 Wh kg-1 on the cell level. This work may shed new light on the understanding of the failure mechanism of SPE for bottom-up improvement of solid-state Li-S batteries.

Multilevel Hollow Phenolic Resin Nanoreactors with Precise Metal Nanoparticles Spatial Location toward Promising Heterogeneous Hydrogenations.

Hollow nanostructures with fascinating properties have inspired numerous interests in broad research fields. Cell-mimicking complex hollow architectures with precise active components distributions are particularly important, while their synthesis remains highly challenging. Herein, a "top-down" chemical surgery strategy is introduced to engrave the 3-aminophenol formaldehyde resin (APF) spheres at nanoscale. Undergoing the cleavage of (Ar)CN bonds with ethanol as chemical scissors and subsequent repolymerization process, the Solid APF transform to multilevel hollow architecture with precise nanospatial distribution of organic functional groups (e.g., hydroxymethyl and amine). The transformation is tracked by electron microscopy and solid-state nuclear magnetic resonance techniques, the category and dosage of alcohol are pivotal for constructing multilevel hollow structures. Moreover, it is demonstrated the evolution of nanostructures accompanied with unique organic microenvironments is able to accurately confine multiple gold (Au) nanoparticles, leading to the formation of pomegranate-like particles. Through selectively depositing palladium (Pd) nanoparticles onto the outer shell, bimetallic Au@APF@Pd catalysts are formed, which exhibit excellent hydrogenation performance with turnover frequency (TOF) value up to 11257 h-1 . This work provides an effective method for precisely manipulating the nanostructure and composition of polymers at nanoscale and sheds light on the design of catalysts with precise spatial active components.

Sulfur stabilizing metal nanoclusters on carbon at high temperatures.

Supported metal nanoclusters consisting of several dozen atoms are highly attractive for heterogeneous catalysis with unique catalytic properties. However, the metal nanocluster catalysts face the challenges of thermal sintering and consequent deactivation owing to the loss of metal surface areas particularly in the applications of high-temperature reactions. Here, we report that sulfur-a documented poison reagent for metal catalysts-when doped in a carbon matrix can stabilize ~1 nanometer metal nanoclusters (Pt, Ru, Rh, Os, and Ir) at high temperatures up to 700 °C. We find that the enhanced adhesion strength between metal nanoclusters and the sulfur-doped carbon support, which arises from the interfacial metal-sulfur bonding, greatly retards both metal atom diffusion and nanocluster migration. In catalyzing propane dehydrogenation at 550 °C, the sulfur-doped carbon supported Pt nanocluster catalyst with interfacial electronic effects exhibits higher selectivity to propene as well as more stable durability than sulfur-free carbon supported catalysts.

Exceptional Electrochemical HER Performance with Enhanced Electron Transfer between Ru Nanoparticles and Single Atoms Dispersed on a Carbon Substrate.

Precisely regulating the electronic structures of metal active species is highly desirable for electrocatalysis. However, carbon with inert surface provide weak metal-support interaction, which is insufficient to modulate the electronic structures of metal nanoparticles. Herein, we propose a new method to control the electrocatalytic behavior of supported metal nanoparticles by dispersing single metal atoms on an O-doped graphene. Ideal atomic metal species are firstly computationally screened. We then verify this concept by deposition of Ru nanoparticles onto an O-doped graphene decorated with single metal atoms (e.g., Fe, Co, and Ni) for hydrogen evolution reaction (HER). Consistent with theoretical predictions, such hybrid catalysts show outstanding HER performance, much superior to other reported electrocatalysts such as the state-of-the-art Pt/C. This work offers a new strategy for modulating the activity and stability of metal nanoparticles for electrocatalysis processes.

Precisely Engineering Architectures of Co/C Sub-Microreactors for Selective Syngas Conversion.

Fischer-Tropsch synthesis (FTS) is an effective route to produce olefins, gasoline, diesel, and oxygenates from syngas (CO + H2 ). However, it still remains a challenge for regulating the product distribution of FTS. Here, a series of Co/C sub-microreactors with precise designed nanoarchitectures are synthesized for selective syngas conversion. Through a combination of surface protection-assisted etching and following carbonization process, Co/C sub-microreactors with solid cube, double-shelled hollow box, and hollow box architectures, namely, Co/C-Cube, Co/C-DBox, Co/C-Box can be obtained. In FTS, comparing with solid Co/C-Cube, double-shelled hollow structured Co/C-DBox is inclined to grow long-chain hydrocarbon products, whereas hollow structured Co/C-Box avails the formation of short-chain hydrocarbon chemicals. Therefore, shape selective catalysis and controlled product distribution of FTS are realized by tuning the architectures of Co/C sub-microreactors. It is expected to fundamentally unravel the heterogeneous catalytic process via upfront designing and precisely regulating the architectures of micro/nanoreactors.

Nitrogen-doped porous carbon-encapsulated copper composite for efficient reduction of 4-nitrophenol.

Developing low-cost non-precious metals as efficient catalysts for the reduction of toxic 4-nitrophenol (4-NP) to useful 4-aminophenol (4-AP) have received increasing attention in recent years. Herein, a novel and efficient Cu-based catalyst Cu/CuxO@CN (carbon doped with nitrogen) was prepared via a facile method from pyrolysis of bi-ligand MOFs material Cu2(BDC)2(BPY) (BDC = p-Phthalic acid, BPY = 4,4'-bipyridyl) in Ar atmosphere. Characterization results revealed that N doping in carbon matrix favors the development of mesoporous structure, the formation of more defect sites in carbon matrix, better dispersion of Cu/CuxO nano particles, and maintenance of Cu species in metallic Cu state (the active site), all of which contribute to a superior catalytic activity for 4-NP reduction with a pseudo-first-order rate constant as high as 0.126 s-1 (the molar ratio of NaBH4 to 4-NP is 400), nearly 11 times higher than its counterpart Cu/CuxO@C without N doping (0.011 s-1). The activation energy for 4-NP reduction to 4-AP catalyzed by Cu/CuxO@CN was determined as 55.6 kJ mol-1 (the molar ratio of NaBH4 to 4-NP is 100). In addition, Cu/CuxO@CN showed excellent reusability in successive 6 cycles. The facile synthesis and superior catalytic activity make Cu/CuxO@CN a promising catalyst in industrial applications for many other similar reaction systems.