Tuning A-Site Cation Deficiency in Pr0.5La0.5BaCo2O5+ δ Perovskite to Realize Large-Scale Hydrogen Evolution at 2000 mA cm-2.

Industrial-level hydrogen production from the water electrolysis requires reducing the overpotential (η) as much as possible at high current density, which is closely related to intrinsic activity of the electrocatalysts. Herein, A-site cation deficiency engineering is proposed to screen high-performance catalysts, demonstrating effective Pr0.5- xLa0.5BaCo2O5+ δ (P0.5- xLBC) perovskites toward alkaline hydrogen evolution reaction (HER). Among all perovskite compositions, Pr0.4La0.5BaCo2O5+ δ (P0.4LBC) exhibits superior HER performance along with unique operating stability at large current densities (J = 500-2000 mA cm-2 geo). The overpotential of ≈636 mV is achieved in P0.4LBC at 2000 mA cm-2 geo, which outperforms commercial Pt/C benchmark (≈974 mV). Furthermore, the Tafel slope of P0.4LBC (34.1 mV dec-1) is close to that of Pt/C (35.6 mV dec-1), reflecting fast HER kinetics on the P0.4LBC catalyst. Combined with experimental and theoretical results, such catalytic activity may benefit from enhanced electrical conductivity, enlarged Co-O covalency, and decreased desorption energy of H* species. This results highlight effective A-site cation-deficient strategy for promoting electrochemical properties of perovskites, highlighting potential water electrolysis at ampere-level current density.

Ligand-Assisted Coordinative Self-Assembly Method to Synthesize Mesoporous ZnxCd1-xS Nanospheres with Nano-Twin-Induced Phase Junction for Enhanced Photocatalytic H2 Evolution.

The designed synthesis of nanotwin architectures and thus-induced phase junctions expresses huge significance for semiconductor photocatalysts. However, current methods of producing nanotwins mainly involve high-temperature thermal treatment and tedious reaction steps, generally resulting in large bulk structure with ill-defined morphology and low specific surface area. Here, we propose a mild ligand-assisted coordinative self-assembly method to synthesize uniform mesoporous ZnxCd1-xS nanospheres with ultrahigh surface areas (148-312 m2 g-1) and controllable diameter (90-370 nm). Moreover, the sample possesses abundant phase junctions induced by nanotwins containing both hexagonal and cubic segments. With the synergy of the twin-induced phase junctions and high surface area, the as-prepared mesoporous Zn0.82Cd0.18S nanospheres exhibit a remarkable photocatalytic H2 evolution rate of 13.46 mmol h-1 g-1 with free noble metal. The mechanism of photocarrier dynamics was studied by transient photovoltage spectroscopy, manifesting that the photocarrier lifetime of Zn0.82Cd0.18S is largely prolonged and therefore improves the charge separation efficiency and photocatalytic activity.

Mesoporous Metal Oxide Encapsulated Gold Nanocatalysts: Enhanced Activity for Catalyst Application to Solvent-Free Aerobic Oxidation of Hydrocarbons.

Here, we present a series of experimental studies to encapsulate ultrasmall gold nanoparticles into mesoporous metal oxide via an in situ self-assembly method. Notably, the 2.0Au@mZnO catalyst (∼2.0 nm gold nanoparticles loading on mesoporous ZnO nanospheres) shows excellent catalytic activity for indane oxidation (120 °C, conversion 88.5%) and affords much high turnover frequencies (9521 h-1). The catalytic activity of these gold-based catalysts was found to be correlated with the size of gold nanoparticles and the types of metal oxide supports. With a decrease in gold nanoparticle size, the catalytic conversion efficiency of indane oxidation increased. In addition, such catalysts possessed high thermal and chemical stability and could be reused more than 10 times without a remarkable loss of catalytic activity.

Wood-converted porous carbon decorated with MIL-101(Fe) derivatives for promoting photo-Fenton degradation of ciprofloxacin.

In response to the escalating concerns over antibiotics in aquatic environments, the photo-Fenton reaction has been spotlighted as a promising approach to address this issue. Herein, a novel heterogeneous photo-Fenton catalyst (Fe3O4/WPC) with magnetic recyclability was synthesized through a facile two-step process that included in situ growth and subsequent carbonization treatment. This catalyst was utilized to expedite the photocatalytic decomposition of ciprofloxacin (CIP) assisted by H2O2. Characterization results indicated the successful anchoring of MIL-101(Fe)-derived spindle-like Fe3O4 particles in the multi-channeled wood-converted porous carbon (WPC) scaffold. The as-synthesized hybrid photocatalysts, boasting a substantial specific surface area of 414.90 m2·g-1 and an excellent photocurrent density of 0.79 µA·cm-2, demonstrated superior photo-Fenton activity, accomplishing approximately 100% degradation of CIP within 120 min of ultraviolet-light exposure. This can be attributed to the existence of a heterojunction between Fe3O4 and WPC substrate that promotes the migration and enhances the efficient separation of photogenerated electron-hole pairs. Meanwhile, the Fe(III)/Fe(II) redox circulation and mesoporous wood carbon in the catalyst synergistically enhance the utilization of H2O and accelerate the formation of •OH radicals, leading to heightened degradation efficiency of CIP. Experiments utilizing chemical trapping techniques have demonstrated that •OH radicals are instrumental in the CIP degradation process. Furthermore, the study on reusability indicated that the efficiency in removing CIP remained at 89.5% even through five successive cycles, indicating the structural stability and excellent recyclability of Fe3O4/WPC. This research presented a novel pathway for designing magnetically reusable MOFs/wood-derived composites as photo-Fenton catalysts for actual wastewater treatment.

Space-Confined Polymerization: Controlled Fabrication of Nitrogen-Doped Polymer and Carbon Microspheres with Refined Hierarchical Architectures.

The construction of refined architectures plays a crucial role in performance improvement and application expansion of advanced materials. The synthesis of carbon microspheres with a refined hierarchical structure is still a problem in synthetic methodology, because it is difficult to achieve the necessary delicate control of the interior structure and outer shell across the microscale to nanoscale. Nitrogen-doped multichamber carbon (MCC) microspheres with a refined hierarchical structure are realized here via a surfactant-directed space-confined polymerization strategy. The MCC precursor is not the traditional phenolic resol but a new kind of 2,6-diaminopyridine-based multichamber polymer (MCP) with a high nitrogen content up to 20 wt%. The morphology and sizes of MCP microspheres can be easily controlled by a dual-surfactant system. The as-synthesized MCC with a highly microporous shell, a multichamber inner core, and beneficial N-doping can serve as a promising supercapacitor material.

A Polymer-Oriented Self-Assembly Strategy toward Mesoporous Metal Oxides with Ultrahigh Surface Areas.

Mesoporous metal oxides (MMOs) have attracted comprehensive attention in many fields, including energy storage, catalysis, and separation. Current synthesis of MMOs mainly involve use of surfactants as templates to generate mesopores and organic reagents as solvents to hinder hydrolysis and condensation of inorganic precursors, which is adverse to adjusting the interactions between surfactants and inorganic precursors. The resulting products have uncontrollable pore structure, crystallinity, and relatively lower surface areas. Here, a facile and general polymer-oriented self-assembly strategy to synthesize a series of MMOs (e.g., TiO2, ZrO2, NbO5, Al2O3, Ta2O5, HfO2, and SnO2) by using cationic polymers as porogens and metal alkoxides as metal oxide precursors in a robust aqueous synthesis system are reported. Nitrogen adsorption analysis and transmission electron microscopy confirm that the obtained MMOs have ultrahigh specific surface areas and large pore volumes (i.e., 733 m2 g-1 and 0.485 cm3 g-1 for mesoporous TiO2). Moreover, the structural parameters (surface area, pore size, and pore volume) and crystallinity can be readily controlled by tuning the interactions between cationic polymers and precursors. The as-synthesized crystalline mesoporous TiO2 exhibits promising performance in photocatalytic water splitting of hydrogen production and a high hydrogen production rate of 3.68 mol h-1 g-1.

A chelation-induced cooperative self-assembly methodology for the synthesis of mesoporous metal hydroxide and oxide nanospheres.

With unique physical and chemical properties and porous architectures, mesoporous transition metal hydroxide (MMHO) and oxide (MMO) nanospheres hold great potential for various applications in drug delivery, catalysis, energy storage and conversion. However, synthesizing MMHO and MMO with well-defined mesostructures remains a great challenge because of the weak interaction between surfactants and metal precursors. Herein we describe a chelation-induced cooperative self-assembly system in which the weak interaction can be cooperatively amplified through the use of a chelating ligand acting as a co-template. Both MMHO and MMO nanospheres with tunable diameters and high surface areas can be readily synthesized via this strategy. The as-synthesized mesoporous ZnO nanospheres exhibit excellent photoelectric performance, and as a highly efficient oxygen evolution reaction (OER) catalyst of low cost, the calcined Cu(OH)2 nanospheres exhibit one of the best activities for the OER. Moreover, this cooperative method gives rise to an alternative to "classical" self-assembly methods for the preparation of mesostructured nanomaterials and, in some cases, the only viable synthetic route toward MMHO and MMO nanostructures.