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Three-dimensionally ordered macro-/mesoporous carbon (OMMC)-supported Ag nanoparticles (Ag/OMMC) with homogeneously dispersed Ag particles are prepared and investigated as effective electrocatalysts for oxygen reduction reaction (ORR) in alkaline aqueous system. The obtained Ag/OMMC catalyst displays smaller Ag particle size, higher Ag dispersion, and enhanced catalytic activity and durability compared with the carbon black Vulcan XC-72R supported Ag (Ag/XC-72R). The sizes of Ag particles supported on the OMMC and XC-72R are 4.3 and 6.5 nm, respectively. The prepared Ag/OMMC catalyst shows a positive half-wave potential of 0.79 V vs. RHE and a large diffusion-limited current of 5.6 mA cm−2 at 0.4 V, superior to Ag/XC-72R catalyst. The better ORR performance of the Ag/OMMC is probably ascribed to the unique 3D ordered interconnected macro-/mesoporous structure, which contributes to facilitating the mass/charge transport, improving the Ag particle dispersion, and preventing the Ag particle growth and aggregation.

In this paper, a novel heat pump system is proposed, which operates as a heat-source-tower heat pump with no frosting in winter, and as a hybrid refrigerant system consisting of a conventional chiller combined with a liquid desiccant dehumidification and evaporative cooling subsystem in summer. A validated mathematical model of the proposed system operating in summer is established to investigate the effects of key parameters, including solution to refrigerant flow ratio (FR), condensation heat recovery ratio (Rcond) and ambient parameters, on the cooling performance. Besides, this paper analyzes key factors that should be considered in designing the heat exchange area of the solution-cooled condenser (SCC). The results show that the maximum COP and ECOP of the heat pump system are 13.4% and 10.3% higher than those of conventional vapor compression refrigerant systems under the typical summer condition of Nanjing, respectively. The recommended range of FR is from 1.2 to 6 and that for Rcond is from 16% to 40%. Moreover, the proposed system is more superior to conventional ones when applied in hot and humid regions.

Cyclic step-catalysis enables intermittent, atmospheric ammonia production, and can be integrated with sustainable and renewable energy sources. By employing metal (e.g., Mn) nitride, a nitrogen ca...

Three-dimensionally (3D) ordered macro-/mesoporous (3DOM/m) materials, which combine the advantages of high surface area of the mesopores, efficient mass transport within the macropores, and strong structural stability of the 3D interconnected porous frameworks, have shown remarkable performances in a wide range of applications. Herein, we demonstrate a novel dual-hard-templating technique as a general synthetic strategy for constructing the 3DOM/m materials by nanocasting mesoporous silica confined within the regular voids of a silica colloidal crystal (opal). Through this method, various materials, such as 3DOM/m Pt, Pd, Ni2P, carbon and N/P codoped carbon (NPC), have been successfully synthesized. The as-prepared 3DOM/m Ni2P and NPC are demonstrated to exhibit outstanding electrocatalytic performance for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), respectively.

Metal-organic frameworks (MOFs) are promising materials for electrocatalysis; however, lack of electrical conductivity in the majority of existing MOFs limits their effective utilization in the field. Herein, an excellent catalytic activity of a 2D copper (Cu)-based conductive MOF, copper tetrahydroxyquinone (CuTHQ), is reported for aqueous CO2 reduction reaction (CO2 RR) at low overpotentials. It is revealed that CuTHQ nanoflakes (NFs) with an average lateral size of 140 nm exhibit a negligible overpotential of 16 mV for the activation of this reaction, a high current density of ≈173 mA cm-2 at -0.45 V versus RHE, an average Faradaic efficiency (F.E.) of ≈91% toward CO production, and a remarkable turnover frequency as high as ≈20.82 s-1 . In the low overpotential range, the obtained CO formation current density is more than 35 and 25 times higher compared to state-of-the-art MOF and MOF-derived catalysts, respectively. The operando Cu K-edge X-ray absorption near edge spectroscopy and density functional theory calculations reveal the existence of reduced Cu (Cu+ ) during CO2 RR which reversibly returns to Cu2+ after the reaction. The outstanding CO2 catalytic functionality of conductive MOFs (c-MOFs) can open a way toward high-energy-density electrochemical systems.

Three-dimensionally ordered mesoporous carbon sphere array (OMCS)-supported Pt nanoparticles (Pt/OMCS) were synthesized and studied as electrocatalysts for the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). In the Pt/OMCS, the Pt particles with a mean size of ∼1.6 nm are homogeneously dispersed on the mesopore walls of the carbon spheres. The Pt/OMCS catalyst exhibits smaller Pt particle size, greater Pt dispersion, larger specific electrochemically active surface area (ECSA), higher activity for MOR and ORR, and better electrocatalytic stability than the carbon black (Vulcan XC-72R)-supported Pt and commercial Pt/C catalysts.

Three dimensionally ordered macro-/mesoporous (3DOM/m) Pt catalysts are fabricated by chemical reduction employing a dual-templating synthesis approach combining both colloidal crystal (opal) templating (hard-templating) and lyotropic liquid crystal templating (soft-templating) techniques. The macropore walls of the prepared 3DOM/m Pt exhibit a uniform mesoporous structure composed of polycrystalline Pt nanoparticles. Both the size of the mesopores and Pt nanocrystallites are in the range of 3–5 nm. The 3DOM/m Pt catalyst shows a larger electrochemically active surface area (ECSA), and higher catalytic activity as well as better poisoning tolerance for methanol oxidation reaction (MOR) than the commercial Pt black catalyst.

Chain-like MoS2 assemblies consisting of hexagonal MoS2 nanoparticles (20–60 nm) have been successfully synthesized in a Triton X-100/cyclohexane/hexanol/water W/O reverse microemulsion in the presence of (NH4)2MoS4 as the molybdenum source and NH2OH·HCl as the reducing agent. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance absorption spectra. The influence of synthetic parameters such as acidity, water/oil ratio (ω0), aging time and annealing temperature on the formation of MoS2 assemblies was investigated. TEM analysis showed that these synthetic factors played important roles in controlling the size of MoS2 nanoparticles and the length of the chain-like MoS2 assemblies. XRD analysis indicated that the well-crystallized MoS2 nanoparticles could be obtained by annealing the precursors at 700°C for 2 h under a flow of N2 atmosphere. In addition, the as-prepared chain-like MoS2 nanoparticles exhibited excellent photocatalytic H2 activity in Ru(bpy)32+-MoS2-H2A three-component molecular systems under visible light irradiation.

High-aspect-ratio of worm-like Ag 2 S nanocrystal with length up to several micrometers and a diameter of 25–50 nm has been successfully prepared by a Triton X-100/cyclohexane/hexanol/water W/O reverse microemulsion in the presence of TAA (Thioacetamide) as a sulfur source and EDTA (ethylene diamine tetraacetic acid) as a chelating ligand. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV–vis diffuse reflectance absorption spectra. The results indicate that the morphology and size of Ag 2 S nanocrystal can be readily controlled by modulating the mole ratio of Ag + to EDTA, the molar ratio of water to surfactant (ω 0 ), and the aging time.

Novel magnetic Co chains with lengths of up to 10–100 μm, self-assembled by cross-linked hexagonal Co microflakes with an average diameter of 2–10 μm and a thickness of about 130 nm, have been solvothermally prepared in the mixed solution of ethylene glycol and ethylenediamine with polyvinyl pyrrolidone (PVP) and dodecanethiol as surfactant. The products were characterized by XRD, EDS, SEM, TEM, HRTEM and SQUID methods. The Co microchains exhibit a ferromagnetic characteristic with the coercivity of 148.8 Oe at room temperature, over fourteen orders of magnitude larger than that of bulk Co counterpart. The simple and high yield synthetic technique can be applied to the fabrication of other metals with complex hierarchical structures.