Heterogeneous Photocatalytic Oxidative Cleavage of Polystyrene to Aromatics at Room Temperature

Heterogeneous photocatalytic aerobic oxidation systems have been developed for selective degradation of polystyrene (PS) to aromatic monomers at room temperature and ambient pressure. The TiO2 particles modified with potassium stearate or N,N-diethyl-3-(trimethoxysilyl)­propan-1-amine photocatalyzed the oxidative cleavage of commercial PS to benzoic acid with up to 43.5 mol % yield. Mechanistic studies revealed that the initial alkyl C–H oxidation and C–C cleavage were greatly improved by these alkaline modifiers. The superoxide anion radical and singlet oxygen acted as the key oxidative species during the degradation process. Common PS waste from daily life also underwent efficient degradation with 18–44.2 mol % yields of benzoic acid on the developed catalysts

Design and Tailoring of the 3D Macroporous Hydrous RuO₂ Hierarchical Architectures with a Hard-Template Method for High-Performance Supercapacitors

In this work, RuO₂ honeycomb networks (RHCs) and hollow spherical structures (RHSs) were rationally designed and synthesized with modified-SiO₂ as a sacrificial template via two hydrothermal approaches. At a high current density of 20 A g^–1, the two hierarchical porous RuO₂·<i>x</i>H₂O frameworks showed the specific capacitance as high as 628 and 597 F g^–1; this is about 80% and 75% of the capacitance retention of 0.5 A g^–1 for RHCs and RHSs, respectively. Even after 4000 cycles at 5 A g^–1, the RHCs and RHSs can still remain at 86% and 91% of their initial specific capacitances, respectively. These two hierarchical frameworks have a well-defined pathway that benefits for the transmission/diffusion of electrolyte and surface redox reactions. As a result, they exhibit good supercapacitor performance in both acid (H₂SO₄) and alkaline (KOH) electrolytes. As compared to RuO₂ bulk structure and similar RuO₂ counterpart reported in pseudocapacitors, the two hierarchical porous RuO₂·<i>x</i>H₂O frameworks have better energy storage capabilities, high-rate performance, and excellent cycling stability

Identification of the Encapsulation Effect of Heteropolyacid in the Si–Al Framework toward Benzene Alkylation

Heterogenization of homogeneous catalysts is a long-term pursuit in the field of catalysis application. Traditional alkylation of arenes with olefins is usually achieved using acid catalysts in a homogeneous system, with high catalytic activity and selectivity but difficulty in catalyst separation and reusability. Herein, H3PW12O40 (HPW), an excellent homogeneous Brønsted acid catalyst, was anchored to the faujasite (FAU) cage of ultrastable Y (USY) zeolite with high dispersion (HPW@USY). 100% conversion of cyclohexene (CHE) with 99.9% yield of cyclohexylbenzene was obtained by the alkylation of benzene (C6H6) and CHE (VC6H6/VCHE= 7:1). No obvious deactivation was observed over HPW@USY after eight cycles. Our experimental and theoretical results demonstrated that W–OH exposed in HPW, encapsulated in the FAU cage, is the active site for alkylation. The excellent performance of the HPW@USY catalyst was attributed to the homogeneous chemical environment and stability of the encapsulated HPW. Benefiting from the formation and stabilization of a reaction intermediate (C6H11•) during the CHE activation, the encapsulation effect of HPW in the Si–Al framework played a significant role in the alkylation between CHE and other aromatic hydrocarbons with high yields of alkylated products. This work provides a promising heterogeneous catalyst strategy, making the alkylation efficiency of aromatics and olefins as high as that of homogeneous catalysts

Cobalt-Ruthenium Nanoalloys Parceled in Porous Nitrogen-Doped Graphene as Highly Efficient Difunctional Catalysts for Hydrogen Evolution Reaction and Hydrolysis of Ammonia Borane

The development of clean fuels for hydrogen utilization will benefit from low-cost and active catalysts to produce hydrogen via hydrolytic dehydrogenation by electrochemical and chemical means. Herein, we designed and synthesized a high-efficiency and stable catalyst with low-ruthenium content CoRu alloy nanoparticles supported on porous nitrogen-doped graphene layers (CoRux@N-C) via pyrolysis of small organic metal molecules. The amount of ruthenium in the catalyst that showed the highest activity was only 5.07 wt %. CoRu0.25@N-C can efficiently catalyze the hydrogen evolution reaction (HER) with a wide pH range and low overpotential to drive current densities of 10 mA·cm–2 of only 27 mV (1.0 M KOH) and 94 mV (0.5 M H2SO4). CoRu0.25@N-C also showed decent durability with negligible degradation after 1000 cyclic-voltammetry cycles in both acidic and alkaline solutions. It also has excellent catalytic activity and can easily sustain ammonia borane hydrolysis with an initial turnover frequency (TOF) of 457.8 molH2 min–1 molcat–1 under ambient conditions. CoRu0.25@N-C can readily perform both NH3­BH3 hydrolytic dehydrogenation and electrochemical hydrogen evolution as a result of its highly specific surface area, carbon layer protection, metal vacancies, and a porous carbon matrix doped with heteroatoms. The creation of a multifunctional composite/hybrid by the use of small metal organic molecules can lead to cost-effective and highly efficient catalysts for energy conversion

Interfacial Effect of CNT-Supported Ultrafine Ru Nanoclusters on Efficient Transfer Hydrogenation of Nitroaromatic Compounds

Carbon nanotube (CNT)-supported ultrafine Ru nanoclusters with adjusted interfacial effects by N-doped carbon (Ru/CNT@CN) were synthesized by a facile ‘impregnation–freeze-drying–thermal reduction’ process. The introduced N-doped carbon not only increased the dispersity of the formed Ru nanoclusters (ultrafine average diameter of about 1.12 nm) but also contributed to obvious electronic transfer from the Ru species to the carbon-based supports (CNT@CN). Profiting from these interfacial effects, Ru/CNT@CN exhibited an excellent turnover frequency (TOF) of 643.6 min–1 for hydrogen production from ammonia borane hydrolysis under neutral conditions at 298 K and a low activation energy of 27.15 kJ mol–1, which was better than that of most Ru-based catalysts. More importantly, the Ru/CNT@CN catalyst showed ultrahigh catalytic activity and halogenated aniline selectivity (>99%) in the transfer hydrogenation of nitroaromatics due to the adsorption and activation of nitroaromatics on positively charged Ru sites, as revealed by density functional theory calculations. This work provides a high-efficiency catalyst for the transfer hydrogenation of nitroaromatics based on the regulation of interfacial effects between Ru nanoclusters and supports

Cobalt Phosphide-Embedded Reduced Graphene Oxide as a Bifunctional Catalyst for Overall Water Splitting

It is highly desirable to design high-efficiency stable and low-price catalysts in the electrocatalysis field. Herein, we reported a cobalt phosphide (Co2P)-loaded reduced graphene oxide (rGO) composite catalyst (rGO/Co2P) prepared via the convenient hydrothermal and H2 reduction methods. The rGO/Co2P catalyst reduced at 800 °C (rGO/Co2P-800) shows superior electrocatalytic activities for hydrogen evolution reaction and oxygen evolution reaction in 1.0 M KOH solution, achieving an overpotential of 134 and 378 mV, respectively, at a current density of 10 mA cm–2. Moreover, the catalyst can not only maintain stability for a long time in alkaline solution but also in acid media because of the protection of the rGO layers. The superior performance of this catalyst is attributed to the synergy between the carbon layer and transition-metal phosphides. The Co2P nanoparticles have a high degree of dispersion, which prevents agglomeration, thereby exposing more active sites. Moreover, rGO protects the exposed metal particles while providing more electroconductivity to the material. This work provides an efficient route for the development of bifunctional electrocatalysts with excellent performance and stability, which provides new ideas toward overall water splitting

Synthesis of Aminopyrene-tetraone-Modified Reduced Graphene Oxide as an Electrode Material for High-Performance Supercapacitors

In this study, we successfully anchored 2-aminopyrene-3,4,9,10-tetraone (PYT-NH₂), a small organic molecule, onto graphene oxide (GO) and then further chemically reduced it to obtain PYT-NH₂/reduced graphene oxide (rGO). We observed that, as an electrode material for high-performance supercapacitor application, PYT-NH₂/rGO exhibited higher capability and smaller charge transfer resistance in comparison with PYT-NH₂/GO, rGO, and PYT-NH₂. The specific capacitances were measured as 326.6 and 229.2 F g^–1 for PYT-NH₂/rGO and PYT-NH₂/GO, respectively, at a current density of 0.5 A g^–1 in 1 M sulfuric acid (H₂SO₄) electrolyte. In addition, we obtained the capacitance of 77.2 F g^–1 for PYT-NH₂/rGO//activated carbon (AC) at 0.5 A g^–1 with an energy density of 15.4 W h kg^–1. Moreover, for the fabricated hybrid capacitor, the capacitance retention of 25 000 cycles was nearly 100% at 5 A g^–1, thus manifesting excellent electrochemical stability and signaling promising potential in energy storage applications

Engineering Interface on a 3D Co_<i>x</i>Ni_1–<i>x</i>(OH)₂@MoS₂ Hollow Heterostructure for Robust Electrocatalytic Hydrogen Evolution

Clarifying the responsibilities and constructing the synergy of different active phases are of great significance but still an urgent challenge for the heterostructure catalyst to improve the hydrogen evolution reaction (HER) process. Here, three-dimensional (3D) CoxNi(1–x)(OH)2 hollow structure integrating MoS2 nanosheet catalysts [CoxNi(1–x)(OH)2@MoS2] were ingeniously designed and prepared. This unique structure has realized the construction of a dual active phase for the optimized stepwise-synergetic hydrogen evolution process over a universal pH range through interface assembly engineering. Meanwhile, the 3D hollow heterostructure with a high surface-to-volume ratio can effectively avoid the agglomeration of MoS2 and enhance the CoxNi(1–x)(OH)2–MoS2 heterointerfaces. Thus, superior HER activity and stability were obtained over the universal pH range. Density functional theory calculation reveals that CoxNi(1–x)(OH)2 and MoS2 phases provide efficient active sites for rate-determining water dissociation and H* adsorption/H2 generation on CoxNi(1–x)(OH)2–MoS2 heterointerfaces, respectively, resulting in an optimized energy barrier for HER. This work proposes a constructive strategy to design highly efficient electrocatalysts based on the heterointerface with a defined responsible active phase of electrocatalysts