Search

Electrochemical reduction of aqueous CO2 into formate is subject to poor selectivity and low current density with conventional Sn-based catalysts owing to the inert nature of CO2 molecules and the low number of active sites. Recently, it has been demonstrated that alkali metal cations could greatly enhance selectivity for CO2 reduction by stabilizing the key intermediates, which leads to an effective solution to this problem by concentrating local metal cations through tailoring the catalyst structure. Herein, we synthesized spiky Cu@Sn nanocones over a macroporous Cu foam, which has a curvature radius of 10 nm, via facile electrochemical coating of a thin layer of Sn over the Cu nanoconic surface. A faradaic efficiency of 90.4% toward formate production was achieved, with a current density of 57.7 mA cm−2 at −1.1 V vs. a reversible hydrogen electrode, which far exceeds results achieved to date with state-of-the-art Sn catalysts. The performance should be attributed to the combined effects of a sharp conical feature that facilitates the enrichment of surface-adsorbed metal cations and the promotion of the mass transfer and active sites growth favored by the three-dimensional porous network.

Here we report a partially oxidized palladium nanodot (Pd/PdOx ) catalyst with a diameter of around 4.5 nm. In aqueous CO2 -saturated 0.5 m KHCO3 , the catalyst displays a Faradaic efficiency (FE) of 90 % at -0.55 V vs. reversible hydrogen electrode (RHE) for carbon monoxide (CO) production, and the activity can be retained for at least 24 h. The improved catalytic activity can be attributed to the strong adsorption of CO2.- intermediate on the Pd/PdOx electrode, wherein the presence of Pd2+ during the electroreduction reaction of CO2 may play an important role in accelerating the carbon dioxide reduction reaction (CO2 RR). This study explores the catalytic mechanism of a partially oxidized nanostructured Pd electrocatalyst and provides new opportunities for improving the CO2 RR performance of metal systems.

Platinum (Pt) nanoparticles below 2 nm loaded on In2O3 nanooctahedra were prepared with the assistance of polymer ligands, and applied as efficient difunctional counter electrode (CE) materials for dye-sensitized solar cells (DSCs). Owing to the excellent light scattering performance of regular nanooctahedra, the light harvesting efficiency was significantly increased, resulting in the noticeable 19.5% enhancement of energy conversion efficiency.

In this work, we prepared a continuous nanostructured Pt-mirror film with metallic lustre and good adhesion to the F-doped tin oxide conducting glass (FTO) substrate through a simple in situ growth method, which retains a good catalytic activity and more importantly, exhibits significant light reflection for light-harvesting. The dye-sensitized solar cells (DSCs) fabricated with Pt-M CE exhibited superior photovoltaic performance compared with the conventional Pt CE. The enhancements of the short-circuit current density and energy conversion efficiency are 15.3% and 18.5%, respectively. Such significant enhancement of the short-circuit current density was found to be related to the excellent light reflection and high catalytic activity of the Pt-M CE. This has been proved by ultraviolet and visible reflection spectra (UV/Vis), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).

The efficient electrocatalysts for many heterogeneous catalytic processes in energy conversion and storage systems must possess necessary surface active sites. Here we identify, from X-ray photoelectron spectroscopy and density functional theory calculations, that controlling charge density redistribution via the atomic-scale incorporation of heteroatoms is paramount to import surface active sites. We engineer the deterministic nitrogen atoms inserting the bulk material to preferentially expose active sites to turn the inactive material into a sufficient electrocatalyst. The excellent electrocatalytic activity of N-In2O3 nanocrystals leads to higher performance of dye-sensitized solar cells (DSCs) than the DSCs fabricated with Pt. The successful strategy provides the rational design of transforming abundant materials into high-efficient electrocatalysts. More importantly, the exciting discovery of turning the commonly used transparent conductive oxide (TCO) in DSCs into counter electrode material means that except for decreasing the cost, the device structure and processing techniques of DSCs can be simplified in future.

Copper phthalocyanine-doped TiO2 microcavities were fabricated by chemistry method. Their spectrum characterization was studied by Fourier transform infrared (FTIR) and Raman spectroscopy, and their fine structure was analyzed by X-ray absorption fine structure (XAFS). The results show that there is interaction of copper phthalocyanine (CuPc) and TiO2 microcavities after TiO2 microcavities was doped with CuPc. For example, there is absorption at 900.76 cm(-1) in FTIR spectra, and the "red shift" of both OH vibration at 3392.75 cm(-1) and CH vibration at 2848.83 cm(-1). There exist definite peak shifts and intensity changes in infrared absorption in the C-C or C-N vibration in the planar phthalocyanine ring, the winding vibration of C-H inside and C-N outside plane of benzene ring. In Raman spectrum, there are 403.4, 592.1 and 679.1 cm(-1) characterized peaks of TiO2 in CuPc-doped TiO2 microcavities, but their wave-numbers show shifts to anatase TiO2. The vibration peaks at 1586.8 and 1525.6 cm(-1) show that there exists the composite material of CuPc and TiO2. These changes are related to the plane tropism of the molecule structure of copper phthalocyanine. XAFS showed tetrahedron TiO4 structure of Ti in TiO2 microcavities doped with copper phthalocyanine, and the changes of inner "medial distances" and the surface structure of TiO2 microcavities.

For Candida rugosa lipase (CRL) catalyzed hydrolysis of racemic 1-phenethyl acetate, both the weakly acidic pH (pH 6.0) and the addition of 1 mM copper (II) ion enhanced the enzyme activity and enantioselectivity (E value) about twofold, as compared with that under neutral pH and noadditive conditions. The decrease of activation free energy (DeltaG) and increase of k(cat)(R)/k(cat)(S) at weakly acidic pH and/or in the presence of copper (II) characterized the kinetic behavior of CRL. On the other hand, for providing reasonable insights into the catalytic mechanism and the structural basis for enantioselectivity alteration, spectroscopic techniques were employed to probe conformational changes of the enzyme in each medium assayed. The fluorescence emission spectra revealed that pH and copper (II) might exert different effects on the microenvironment of Trp residue and thereby on the protein conformation, which could be further verified by UV-visible and Raman spectra. The conformational modulation of CRL associated with either pH or copper (II) concentration in the reaction medium could be attributed to the flexible and sensitive conformation of the enzyme, which is responsible for the significant variation of apparent activity and enantioselectivity with the tuning of biocatalyst microenvironment.

To study the spectral characteristic of TiO2/SnO2, TiO2/SnO2 composite oxide with SnO2 inside kernel was fabricated by colloid chemistry method, and was studied with UV-visible absorption spectrum, X-ray diffraction and infrared spectrum. The results showed that the bandgap widths of TiO2 and TiO2/SnO2 were 4.13 and 3.86 eV, respectively. TiO2/SnO2 had a widest and strong absorption band in the ultraviolet range. There was a quantum effect. In the X-ray diffraction, the station of TiO2 (110) diffraction peak moved 1.6 degrees, and its intensity changed. Compared with TiO2 infrared spectrum, the Ti--O stretching vibration of TiO2/SnO2 moved from 500 to 656 cm(-1), and had 560 cm(-1) shoulder peak. The intensity of the peaks near 1 650 and 3 420 cm(-1) corresponding to water absorbing peaks increased.

The alpha-Fe2O3 ultrafine particles were equally dispersed in the solutions of stearic acid/n-hexane/chloroform by the ultrasonic method, the surfaces of the alpha-Fe2O3 ultrafine particles were decorated by stearic acid, and the alpha-Fe2O3 ultrafine particles decorated had very good flowage characteristic. Before alpha-Fe2O3 ultrafine particles were decorated, the UV absorption was very strong at wavelengths shorter than 290 nm, and there was a shoulder peak at 330 nm. The absorption band edges of alpha-Fe2O3 ultrafine particles was at 392 nm, and shifted toward blue, which was in contrast with that of bulk Fe2O3. This was caused by the quanta size effect and surface effect. IR characteristic peaks of the alpha-Fe2O3 ultrafine particles appeared at 524.36 and 446.37 cm-1. After alpha-Fe2O3 ultrafine particles were decorated, the absorption side moved from 392 to 896 nm, which significantly shifted to the red in contrast with that of bulk F2O3. The vibration of Fe-O bond moved from 524.36 to 521.33 cm-1 and from 446.37 to 443.34 cm-1, respectively. These were caused by the dielectric confinement effect. The relative intensity of X-ray diffraction obviously increased, and the diffraction peak size moved toward the direction of smaller diffraction angle after the alpha-Fe2O3 ultrafine particles were decorated.