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Rational tuning the surface charge state for catalysts is an attractive strategy to promote their catalytic activity toward catalyzing diverse chemical and electrochemical reactions. In this work, we modified the surface of a pure tungsten carbide (WC) material with an ultra-thin nitrogen doped carbon (NC) layer (WC@NC) for catalyzing alkaline hydrogen evolution reaction (HER). The XPS studies revealed an increased electron density on WC when the NC layer was introduced on its surface. Thus, a significant decrease of 282 mV in overpotential at 10 mA cm−2 was observed on WC@NC electrode in comparison with the pristine WC electrode. The higher electrochemical active surface area, lower activation energy barrier, and excellent durability were identified by various electrochemical measurements. The three-dimensional charge density difference was also calculated and the results indicated that an electron-transfer process occurred from the NC layer (donor) to the WC layer (acceptor) through the interface of WC@NC composite material. The analysis explained the underlying mechanism for the promotion of the HER activity. Such a comprehensive study is expected to provide useful guidance for promoting the catalytic performance of diverse catalysts toward different reactions.

TiO2 can be integrated with antimony-doped tin oxide to obtain composite materials with high electroconductivity. Based on this, spherical TiO2@Sb–SnO2 (TSS) has been prepared by homogeneous precipitation combined with a high-temperature calcination process. The morphology, structure and composition of TSS were characterized by scanning electron microscope, Brunauer–Emmet–Teller surface area analyzer, X-ray diffractometer and transmission electron microscope with energy-dispersive X-ray spectrometer, respectively. Effects of dropping conditions, introducing sulfate, pH value, calcination temperature and holding time on the conductivity of TSS were investigated by measuring resistivity, Zeta potential and particle size, meanwhile the calcination action and conductive mechanism by thermogravimetric analysis, X-ray photoelectron spectroscopy and electron spin resonance. The results revealed that the core–shell structured TSS was formed, and the resistivity of composite powder was below 4.0 Ω cm under the optimum conditions. Our analysis indicates that the conductive channel mechanism is the main conductive mechanism of the as-prepared composite.

A series of novel nonmetallic plasmonic materials, indium tin oxide (ITO) nanocrystals (NCs), with tunable doping ratios of tin (from 0 up to 25%), were synthesized through a one-step solvothermal method. Cubic-shaped NCs with good crystallinity and uniform-size distribution (~ 17 nm), for all doping ratios, were confirmed through the X-ray diffraction patterns and transmission electron microscopy images. As inferred from X-ray photoelectron spectroscopy and inductively coupled plasma measurements, Sn is preferentially distributed close to the surface of ITO NCs. In particular, localized surface plasmon resonances (LSPRs) were tuned from near- to mid-infrared regions only by varying the doping ratios, which is of interest, for example, to avoid high-loss levels associated with metallic nanoparticles in LSPR biosensing applications. Our work provides a series of reliable and accessible materials for the researchers who need different wavelengths of LSPR frequencies in near-infrared and/or mid-infrared regions. It will benefit the research and development of nonmetallic plasmonic materials in a wider application scope.

By varying divalent-metal cations (M = Mg2+, Ni2+, Cu2+, Zn2+) with different d-bands classification, MAl-LDHs were prepared and inspected for solar-driven CO2 conversion. The CO and CH4 yields over these LDHs followed an order of: NiAl-LDHs > CuAl-LDHs > ZnAl-LDHs > MgAl-LDHs. Coupled with multiple characterizations, the activity distinction was revealed from three crucial perspectives: (i) light harvesting, (ii) charge separation and transfer, (iii) surface reactions. The results affirmed that when d orbital was partially occupied with active electrons, both activation of CO2 and excitation of electrons were much easier to achieve. In-situ DRIFTS manifested that NiAl-LDHs and CuAl-LDHs exhibited more active reaction with CO2, which may be related to the upward shifts of the d-band center determined by Valence-band XPS. Particularly, these LDHs exhibited various catalytic stabilities, which was explained by Pearson׳s hard and soft acid–base (HSAB) principle for the first time in this field.

In this study, magnetic Fe3O4 nanoparticles (MNP) modified with O-phosphorylethanolamine (O-PEA) were successfully prepared by non-thermal plasma induced method with different treatment times. The raw and modified MNP were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrophotometer (FT-IR), and vibration sample magnetometer (VSM). The modified MNP samples show higher adsorption capacity for U(VI) removal and longer treatment time results in higher adsorption capacity and efficiency. The experimental parameters were optimized by means of the response surface methodology to improve the removal efficiency of U(VI) by the modified adsorbents from aqueous solutions. The O-PEA modified MNP with 120 min treatment time shows the highest adsorption capacity with 228.17 mg⋅g−1 among the five samples at 293.15 K. Thermodynamic studies reveal that the adsorption process of U(VI) onto O-PEA modified MNP is endothermic and spontaneous. XPS studies indicate that the U(VI) removal is fulfilled through the binding interactions between U(VI) and NH2, OH and phosphate groups on the modified MNP surface. This work not only provides a simple, convenient and cost-effective way for water treatment by plasma modification, but also provides a new insight into preparing promising adsorbents to achieve magnetic separation from aqueous solution.

In this paper, a series of catalysts about CeO2 active sites prepared using reduced TiO2 (TiR) as supports were firstly used for selective catalytic reduction (SCR) of NO by NH3. The catalytic performance evaluation results showed that the NO removal efficiency of CeO2/TiR (CeTiR) was much higher than that of CeO2/TiO2 (CeTi). Hence, the aim of this study was to investigate the promotion mechanism of catalytic performance of CeTiR catalysts. The catalysts were characterized by XRD, BET, Raman, XPS, NH3-TPD and H2-TPR. The results of characterization revealed that CeO2 had a strong interaction with oxygen vacancies of TiR supports. The strong interaction resulted in more Ce3+ formation and better redox properties for CeTiR catalysts. In addition, it was confirmed that the better redox properties of CeTiR could be considered as the major reason of its high SCR activity via L-H mechanism but not acid properties. We expected that this study could shed some lights on the development of SCR catalysts for improving the interaction between Ti support and active species for enhancing SCR reaction.

This study aimed at investigating the photocatalytic oxidation removal of NO from the flue gas of coal-fired boilers by H2O2/UV (UV is ultraviolet radiation) reaction over TiS catalyst. The effects of different catalysts and gas composition on the oxidation of NO were investigated. We found that the S doped titania (TiO2) catalyst could clearly improve the NO oxidation, compared with TiO2 and no catalyst in the H2O2/UV system. In addition, the H2O2 and UV also played an important role in the NO oxidation. The NO oxidative product was the stable nitrate. Analysis of catalysts' characterization by XRD, TEM, XPS, UV–vis and DFT calculations showed that the S (S6+) doped TiO2 catalyst included the heterostructure of Ti1−xSxOx+2 compounds and TiO2. The S doping increased the VB potential for the TiS catalyst. We designed different tests of PL, LSV, EPR liquid UV–vis analysis-PCBA and RhB to confirm the mechanism of enhanced NO oxidation over TiS catalyst. It was found that the reactions in the VB were important to the NO oxidation over the TiS(TiO2)+UV+H2O2 catalytic system. Due to this reason, enhanced NO oxidation was achieved over the TiS catalyst.

Herein, a type-Ⅱ heterojunction of Zn0.2Cd0.8S/g-C3N4 (ZnCdS/CN) nanocomposites for CO2 photoreduction to produce CH3OH is prepared via a combined simple sonication and hydrothermal method. After introducing g-C3N4 into Zn0.2Cd0.8S, it is found that the amorphous powder g-C3N4 is coated on the surface of Zn0.2Cd0.8S. The HRTEM and XPS results illustrate the heterostructure formation. The i-t curve, EIS and PL results suggest that the formed type-Ⅱ heterojunction improves the charge separation and transfer efficiency, and inhibits the recombination of photoinduced electron-hole pairs. Because of the improved photoelectric performance brought by the heterojunction, an optimized sample with g-C3N4 to ZnCdS/CN mass ratio of 30% displays high CH3OH production rate of 11.5 ± 0.3 μmol·g−1·h−1, which is 2.6 and 2.7 times greater than that of Zn0.2Cd0.8S solid solution (4.4 ± 0.2 μmol·g−1·h−1) and g-C3N4 (4.2 ± 0.1 μmol·g−1·h−1), respectively. Moreover, under the protection of g-C3N4, the crystal structure and reaction activity of the composite are almost maintained even after four cycles, showing excellent stability. This work can provide guidance for synthesis of other heterojunction photocatalysts with excellent activity and stability.

Organic semiconductor-based electrode materials are promising candidates for energy storage devices due to their high capacity, excellent flexibility, low cost and resource sustainability. The alkali metal storage mechanisms on various active functional groups of the organic materials, however, are still not clear at the molecular scale. It is essential to conduct systematic mechanism studies for the alkali storage behaviors in organic electrode materials. Here, the chemical and electronic structure evolutions upon the deposition of lithium (Li) and sodium (Na) on a model organic semiconductor electrode material of perylene-3,4,9,10-tetracarboxylicdianhydride (PTCDA), have been investigated by in-situ x-ray photoemission spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), near edge x-ray absorption fine structure (NEXAFS) spectroscopy and density functional theory (DFT) calculations. It reveals that Li/Na can react with the carbonyl oxygen and increase the electron density within the PTCDA perylene. Moreover, the band-bending like features are observed on PTCDA film upon Li/Na interaction. Our experimental results and theoretical calculations indicate that reactions on carbonyl groups and charge redistribution are crucial for the Li/Na storage process, which shed light on comprehensive insights for the Li/Na storage behaviors on organic semiconductor-based electrode materials. Ministry of Education (MOE) Authors acknowledge the financial support from Singapore MOE grant R143-000-A29-112 and Academic Research Fund Tier 1 (RG104/ 18), as well as the computing resources from National Supercomputing Centre Singapore.

A ZnO/CdS/Cu2S composite photocatalyst with high photocatalytic activity was successfully synthesized by a three-step process. The results of XRD, XPS, SEM, and UV–Vis analysis show that ZnO nanosheets were successfully compounded with CdS nanoparticles, and the surface of CdS was successfully modified by Cu2S under ultraviolet light. Photocatalytic measurements were carried out and the results show that the photocatalytic efficiency of ZnO/CdS/Cu2S reached 95%. Compared with ZnO ([Formula: see text][Formula: see text][Formula: see text]), the kinetic constant of ZnO/CdS/Cu2S was up to [Formula: see text][Formula: see text][Formula: see text], which shows its excellent photocatalytic activity. A photocatalytic mechanism was proposed to illustrate the high activity separation efficiency.

Basic lithium phosphate catalysts for the rearrangement of propylene oxide can be easily deactivated due to carbon deposits. In-situ DRIFTS, TG–DTG, NMR and XPS were used to study carbon deposits. Results showed that carbon deposits were mainly in the form of C x H y and C x H y O, which could be decomposed in a mixture of N 2 and O 2 atmosphere at higher than 300 °C or in N 2 atmosphere near 500 °C. A shorter period of time was needed in the atmosphere containing O 2 .

A simple and efficient heterogeneous palladium catalyst was prepared for aromatic ring hydrogenation. The catalyst was prepared by a reduction-deposition method and exhibited high activity and selectivity for the hydrogenation of a variety of substituted aromatic compounds to the corresponding cyclohexane and cyclohexanol derivatives with up to 99% yields. The catalyst was characterized by BET, TEM, XRD, XPS and ICP. Meanwhile the reusability of the catalyst was investigated, and it can be reused for several runs without significant deactivation.