Three-Dimensional Porous Cu/Cu2+1O Nanosheet Arrays Promote Electrochemical Nitrate-to-Ammonia Conversion.

The efficiency of electrochemical nitrate (NO3-) reduction to ammonia (NH3) still remains a challenge due to the sluggish kinetics of the complex eight-electron reduction process and competitive hydrogen evolution reaction (HER). Herein, we designed new three-dimensional (3D) porous Cu/Cu2+1O nanosheet arrays (Cu/Cu2+1O NSA) by coupling a template-directed method with in situ electroreduction. Thanks to the 3D porous structure and in-plane heterojunctions, Cu/Cu2+1O NSA can provide abundant active sites and a good interfacial effect, obtaining the maximum Faradaic efficiency (FE) of ammonia (88.09%) and high yield rate of 0.2634 mmol h-1 cm-2, which is higher than that of CuO nanosheets (77.81% and 0.2188 mmol h-1 cm-2) and CuO nanoparticles (34.60% and 0.0692 mmol h-1 cm-2). Experimental results and DFT simulations show that the interface effect of Cu/Cu2+1O can decrease the reaction energy barrier of the key step (*NO to *NOH) and can greatly inhibit the competitive hydrogen evolution reaction, thereby achieving excellent electrocatalytic performance for nitrate-to-ammonia conversion.

Design and synthesis of 'single-crystal-like' C-doped TiO2 nanorods for high-performance supercapacitors.

Although TiO2 is widely used as a promising electrode material for supercapacitors, its potential application suffers from a critical limitation due to its poor electrical conductivity and low rate capability. Here, we report a cost-effective hydrothermal strategy to design and construct a novel 'single-crystal-like' C-doped TiO2 electrode material. The as-synthesized electrode material combines the advantages of TiO2, 'single-crystal-like' features and carbon doping, considerably improving the electrical conductivity of TiO2. The electrochemical measurements demonstrate that the C-doped TiO2 material presents an excellent specific capacitance (449.8 F g-1 at 1 A g-1), which approaches six times more than the value (77.3 F g-1 at 1 A g-1) of P25 electrodes, and far beyond the value of many previously reported TiO2 electrodes. Therefore, this work explores a new method to design high performance electrochemical TiO2 electrode materials by incorporating other dopants into the TiO2 lattice.

Metal Nanoparticles Confined within an Inorganic-Organic Framework Enable Superior Substrate-Selective Catalysis.

The search for catalysts with a perfect substrate selectivity toward the hydrogenation of nitroarenes is a goal of high importance, which still remains a significant challenge. Here, we designed a new type of catalyst with superior substrate selectivity by combining a space-confined effect and a hydrogen-bonding network, in which metal nanoparticles (MNPs) were confined in hierarchical hollow silica (HHS) with a poly(N-isopropylacrylamide) (PNIPA) coating. Given the strong induced properties of hydrogen-bond donors and acceptors in the HHS support and PNIPA coating, the as-synthesized catalyst would achieve perfect substrate selectivity for the hydrogenation of various nitroarenes and their mixture by thoroughly impeding the reduction of nitroarenes with any hydroxyl or carboxyl groups, which is typically very difficult to be realized over almost all of the reported supported-metal catalysts. Notably, the hydrogenation of nitroarenes can produce almost quantitative yields of anilines over the as-synthesized catalyst. Furthermore, density functional theory and experimental evidence are also provided for the hierarchical structure of HHS and PNIPA coating associated with substrates to demonstrate how a substrate could have access or be blocked into the confined active centers (MNPs). Therefore, this work would open a new window to design efficient catalysts for a wide variety of substrate-selective catalyses.

Hierarchically-structured SiO2-Ag@TiO2 hollow spheres with excellent photocatalytic activity and recyclability.

A new protocol for constructing sandwich-like SiO2-Ag@TiO2 hollow spheres (SAT) is introduced, in which SiO2 acts as an efficient support for the Ag nanoparticles (Ag NPs) immobilization, while TiO2 maintains its hierarchical structure and prevents the aggregation of Ag NPs during the photocatalytic reaction. As a photocatalytic agent, the inner and outer surfaces of TiO2 can be fully occupied by pollutants molecules because of its unique structure, which faster boosts the photo-generated electrons to transfer the substrates, leading to an enhanced photocatalytic performance. Compared with Ag NPs deposited on the surface of SiO2@TiO2 (STA), the as-synthesized SAT exhibits a markedly enhanced visible-light and UV light activity than STA for degrading tetracycline and traditional dyes. The excellent photocatalytic performances are ascribed to the enhanced transport paths of photo-generated electrons, reduced recombination probability of e-/h+ pairs, and decreased threat of oxidation and corrosion. Especially, the SAT still maintains its photocatalytic efficiency after five consecutive runs even though the sample is recovered under visible-light irradiation, far beyond the reusability of STA under the same conditions. Therefore, the outstanding photocatalytic activity and excellent recyclability make SAT more potential to purify aquatic contaminants and to meet the demands of future environmental issues.