Phase-Selective Syntheses of Cobalt Telluride Nanofleeces for Efficient Oxygen Evolution Catalysts

Cobalt-based nanomaterials have been intensively explored as promising noble-metal-free oxygen evolution reaction (OER) electrocatalysts. Herein, we report phase-selective syntheses of novel hierarchical CoTe₂ and CoTe nanofleeces for efficient OER catalysts. The CoTe₂ nanofleeces exhibited excellent electrocatalytic activity and stablity for OER in alkaline media. The CoTe₂ catalyst exhibited superior OER activity compared to the CoTe catalyst, which is comparable to the state-of-the-art RuO₂ catalyst. Density functional theory calculations showed that the binding strength and lateral interaction of the reaction intermediates on CoTe₂ and CoTe are essential for determining the overpotential required under different conditions. This study provides valuable insights for the rational design of noble-metal-free OER catalysts with high performance and low cost by use of Co-based chalcogenides.     

CoMn@NC催化5-羟甲基糠醛常压氧化为2, 5-呋喃二甲酸二甲酯

Dimethyl furan-2, 5-dicarboxylate (DMFDCA) is a valuable biomass-derived chemical that is an ideal alternative to fossil-derived terephthalic acid as a monomer for polymers. The one-step oxidation of 5-hydroxymethylfurfural (HMF) to DMFDCA is of practical significance. It not only shortens the reaction pathway but also avoids the separation process of intermediates; thus, reducing cost. In this work, non-noble bimetallic catalysts supported on N-doped porous carbon (CoMn@NC) were synthesized via a one-step co-pyrolysis procedure using different pyrolysis temperatures and proportions of metal precursors and additives. We employed the prepared CoMn@NC catalysts in the aerobic oxidation of HMF under mild reaction conditions to obtain DMFDCA. High-yield DMFDCA was obtained by screening the prepared catalysts and optimizing the reaction conditions, including the strength and amount of the base, as well as the reaction temperature. The optimized yield of DMFDCA was 85% over the Co₃Mn₂@NC-800 catalyst after 12 h at 50 ℃ using ambient-pressure oxygen. The physicochemical properties of the catalysts were determined using a variety of characterization techniques, the factors affecting the performance of each catalyst were investigated, and the relationship between the physicochemical properties and performance of the prepared catalysts was elucidated. A porous structure with a high surface area had a positive effect on mass transfer efficiency. Cobalt nanoparticles (NPs) and atomically dispersed Mn were coordinated to N-doped carbon to form M―N_x (where M = Co or Mn). Based on the Mott-Schottky effect, there was significant electron transfer between each metal and the N-doped carbon, additionally, the metal NPs supplied electrons to the carbon atoms. The electron-deficient metal site in the pyridinic N-rich carbon was beneficial for the activation of HMF and oxygen. The activation of oxygen produced reactive oxygen species (such as superoxide radical anions) to ensure high selectivity to DMFDCA through dehydrogenative oxidation of the hemiacetal intermediate and hydroxymethyl group of 5-hydroxymethyl-2-methyl-furoate. The existence of disordered and defective carbons increased the number of active sites. Subsequently, we performed a series of control experiments. Based on our current experimental results and previous studies, we propose a simple mechanism for the aerobic oxidation of HMF to DMFDCA. The catalyst was stable, its performance decreased slightly after two cycles, and it was tolerant to SCN⁻ ions and resistant against N or S poisoning. Furthermore, the use of this catalytic system can be expanded to various substituted aromatic alcohols, such as benzyl alcohols with different substituents, furfuryl alcohol, and heterocyclic alcohols. Simultaneously, the product type was further extended from methyl esters to ethyl esters with a high yield when the substrate reacted with ethanol. In conclusion, this catalytic system can be applied in the production of carboxylic esters for polymers.     

Designing Solid Electrolyte Interfaces towards Homogeneous Na Deposition: Theoretical Guidelines for Electrolyte Additives and Superior High-Rate Cycling Stability

Metallic Na is a promising metal anode for large-scale energy storage. Nevertheless, unstable solid electrolyte interphase (SEI) and uncontrollable Na dendrite growth lead to disastrous short circuit and poor cycle life. Through phase field and ab initio molecular dynamics simulation, we first predict that the sodium bromide (NaBr) with the lowest Na ion diffusion energy barrier among sodium halogen compounds (NaX, X=F, Cl, Br, I) is the ideal SEI composition to induce the spherical Na deposition for suppressing dendrite growth. Then, 1,2-dibromobenzene (1,2-DBB) additive is introduced into the common fluoroethylene carbonate-based carbonate electrolyte (the corresponding SEI has high mechanical stability) to construct a desirable NaBr-rich stable SEI layer. When the Na||Na₃V₂(PO₄)₃ cell utilizes the electrolyte with 1,2-DBB additive, an extraordinary capacity retention of 94 % is achieved after 2000 cycles at a high rate of 10 C. This study provides a design philosophy for dendrite-free Na metal anode and can be expanded to other metal anodes.     

Tuning the CO2 Hydrogenation Selectivity of Rhodium Single-Atom Catalysts on Zirconium Dioxide with Alkali Ions

Tuning the coordination environments of metal single atoms (M₁) in single-atom catalysts has shown large impacts on catalytic activity and stability but often barely on selectivity in thermocatalysis. Here, we report that simultaneously regulating both Rh₁ atoms and ZrO₂ support with alkali ions (e.g., Na) enables efficient switching of the reaction products from nearly 100 % CH₄ to above 99 % CO in CO₂ hydrogenation in a wide temperature range (240–440 °C) along with a record high activity of 9.4 mol_CO g_Rh⁻¹ h⁻¹ at 300 °C and long-term stability. In situ spectroscopic characterization and theoretical calculations unveil that alkali ions on ZrO₂ change the surface intermediate from formate to carboxy species during CO₂ activation, thus leading to exclusive CO formation. Meanwhile, alkali ions also reinforce the electronic Rh₁-support interactions, endowing the Rh₁ atoms more electron deficient, which improves the stability against sintering and inhibits deep hydrogenation of CO to CH₄.     

Metal-Organic Frameworks for Photocatalytic Water Splitting and CO2 Reduction

Photocatalytic water splitting and carbon dioxide (CO₂) reduction provide promising solutions to global energy and environmental issues. In recent years, metal-organic frameworks (MOFs), a class of crystalline porous solids featuring well-defined and tailorable structures as well as high surface areas, have captured great interest toward photocatalytic water splitting and CO₂ reduction. In this review, the semiconductor-like behavior of MOFs is first discussed. We then summarize the recent advances in photocatalytic water splitting and CO₂ reduction over MOF-based materials and focus on the unique advantage of MOFs for clarifying the structure-property relationship in photocatalysis. In addition, some representative characterization techniques have been presented to unveil the photocatalytic kinetics and reaction intermediates in MOF-based systems. Finally, the challenges, and perspectives for future directions are proposed.     

A Petrochemical-Free Route to Superelastic Hierarchical Cellulose Aerogel

Cellulose aerogels are plagued by intermolecular hydrogen bond-induced structural plasticity, otherwise rely on chemicals modification to extend service life. Here, we demonstrate a petrochemical-free strategy to fabricate superelastic cellulose aerogels by designing hierarchical structures at multi scales. Oriented channels consolidate the whole architecture. Porous walls of dehydrated cellulose derived from thermal etching not only exhibit decreased rigidity and stickiness, but also guide the microscopic deformation and mitigate localized large strain, preventing structural collapse. The aerogels show exceptional stability, including temperature-invariant elasticity, fatigue resistance (∼5 % plastic deformation after 10⁵ cycles), high angular recovery speed (1475.4° s⁻¹), outperforming most cellulose-based aerogels. This benign strategy retains the biosafety of biomass and provides an alternative filter material for health-related applications, such as face masks and air purification.     

Two-dimensional Supramolecular Polymers Based on Selectively Recognized Aromatic Cation-π and Donor-Acceptor Motifs for Photocatalytic Hydrogen Evolution

Two-dimensional (2D) organic polymers have recently received considerable interest, especially those whose architectures are held together via supramolecular engineering. However, current approaches toward supramolecular 2D structures usually suffer from mutual interference of noncovalent interactions and lack of intrinsic functions. Herein, we report well-regulated 2D supramolecular polymers (2DSPs) through an aromatics-selective recognition strategy of cation-π and donor-acceptor (D-A) motifs, which are derived from C₄-symmetric cationic monomers and electron-withdrawing molecules. By subtly designing the strength and direction of noncovalent driving forces, the mutual interference between cation-π and D-A interactions is effectively avoided, enabling the construction of 2DSPs in aqueous solution. On this basis, the resultant 2DSPs possess boosted photocatalytic hydrogen evolution activity at a rate of 600 μmol g⁻¹ h⁻¹, which is mainly ascribed to the specific stacking mode of cation-π/D-A motifs and the ordered 2D structures.     

Ferric Single-Site Catalyst Confined in a Zeolite Framework for Propane Dehydrogenation

Non-oxidative dehydrogenation of propane is a highly efficient approach for industrial preparation of propene that is commonly catalyzed by noble Pt or toxic Cr catalysts and suffers from coking. In this work, ferric catalyst confined in a zeolite framework was synthesized by a hydrothermal procedure. The isolated Fe in the framework formed distorted tetrahedra, which were beneficial for the selective dehydrogenation of propane and reached over 95 % propene selectivity and over 99 % total olefins selectivity. This catalyst had a silanol-free structure and was oxygen tolerant, hydrothermally stable, and coke free, with a deactivation constant of 0.01 h⁻¹. This study provided guidance for the synthesis of structural heteroatomic zeolite and efficient propane non-oxidative dehydrogenation over early transition metals.     

Promoting Photocatalytic H2 Evolution through Retarded Charge Trapping and Recombination by Continuously Distributed Defects in Methylammonium Lead Iodide Perovskite

Inspired by its great success in the photovoltaic field, methylammonium lead iodide perovskite (MAPbI₃) has recently been actively explored as photocatalysts in H₂ evolution reactions. However, the practical application of MAPbI₃ photocatalysts remains hampered by the intrinsically fast trapping and recombination of photogenerated charges. Herein, we propose a novel strategy of regulating the distribution of defective areas to promote charge-transfer dynamics of MAPbI₃ photocatalysts. By deliberately designing and synthesizing the MAPbI₃ photocatalysts featuring a unique continuation of defective areas, we demonstrate that such a feature enables retardation of charge trapping and recombination via lengthening the charge-transfer distance. As an outcome, such MAPbI₃ photocatalysts turn out to achieve an impressive photocatalytic H₂ evolution rate as high as 0.64 mmol ⋅ g⁻¹ ⋅ h⁻¹, one order of magnitude higher than that of the conventional MAPbI₃ photocatalysts. This work establishes a new paradigm for controlling charge-transfer dynamics in photocatalysis.