•The mechanically stable Au/r-GO/TNTs electrode was fabricated.•The electrode showed an ultra-high sensitivity and low detection limitation for H2O2 sensing.•The electrode was enzymeless but showed excellent selectivity.•The Au/r-GO/TNTs electrode was also very sensitive to dissolved O2 and nitrite ions.Au nanoparticles and reduced graphene oxide (r-GO) co-modified TiO2 nanotube arrays (TNTs) were prepared by a facile and green strategy based on the electro-deposition technology for detecting H2O2, O2 and nitrite. As-prepared Au/r-GO/TNTs electrode was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results clearly demonstrate that the successful attachment of r-GO sheets and narrow-range distribution of Au nanoparticles on TNTs. The reduced grapheme oxide sheet can help to improve the electronic conductive performance of TNTs and prevent the agglomeration of Au nanoparticles. Electrochemical studies reveal that the Au/r-GO/TNTs electrode exhibit excellent electrocatalytic performance toward the reduction of H2O2. Under the optimal experimental condition, the sensor has a quick response to H2O2 at −0.3 V with a high sensitivity (1011.35 mA M−1 cm−2), wide linear range (0.01–22.3 mM) and low detection limit (0.006 μM). In addition, the sensor also has good stability and excellent selectivity. Moreover, the established Au/r-GO/TNTs electrode also shows high sensitivities towards dissolved O2 and nitrite ions, which has great potential for the development of electrochemical sensors, molecular bioelectronics devices and biosensors.

The extinction peak of Pd particles generally locates at the ultraviolet light region, suggesting that only 4% of solar light can be absorbed. Furthermore, the efficiency of LSPR hot electrons converted to chemical energy of reaction is very low due to the fast relaxation of carriers. It is extremely valuable to design Pd-based catalysts which have strong response to the visible light irradiation and high efficiency in photon to chemical energy. The Pd–CeO2 catalyst was synthesized via the hexadecyltrimethylammonium bromide (CTAB) assisted liquid-phase reduction method to generate more active interfaces. The significant extinction of Pd–CeO2 in the visible to near-infrared region indicates the strong electron interaction between Pd and CeO2. LSPR hot electrons, transferring from the Pd metal particles to the conduction band of ceria, promote the dissociation of adsorbed oxygen. Therefore, the reaction temperature of CO and toluene oxidation can be significantly lowered by visible light irradiation. The maximum light efficiencies of Pd–CeO2 catalyst for toluene oxidation and CO oxidation are obtained as 0.42% and 1%, which benefit from the effective Pd–O–Ce interfaces.

A ZP/CZ (zirconium phosphate/Ce0.5Zr0.5O2) catalyst exhibits over 80% NOx conversion from 250 to 450 °C under a high GHSV of 300000 h−1 in the presence of H2O, CO2 and C3H8. Mixing with soot leads to a decrease in NOx conversion of the catalyst at temperatures higher than 350 °C. After hydrothermal aging (760 °C for 48 h) and sulfur aging (400 °C for 48 h), ZP/CZ still possesses over 80% NOx conversions in 289–450 °C and 297–466 °C respectively, which are significantly better than those of home made Cu-SAPO-34 and vanadium catalysts at higher temperatures. These results indicate that ZP/CZ is a promising catalyst for NOx abatement for diesel engine exhausts.

•Hierarchical porous γ-Al2O3 hollow microspheres were synthesized.•The mechanism for obtaining the γ-Al2O3 hollow microspheres containing macro-meso-micropores was proposed.•NH4Cl was demonstrated to be a template to act as the core and prevents the aggregation of laminar boehmites.•High adsorption capacity and adsorption rate of hierarchical porous γ-Al2O3 hollow microsphere for Congo Red.Hierarchical porous γ-Al2O3 hollow microspheres were synthesized by a modified spray drying method. Ageing the precipitated precursor and spray-drying assisted by NH4Cl salts are considered as two key steps for the synthesis of γ-Al2O3 hollow microspheres. The mechanism of the formation of hierarchical porous γ-Al2O3 hollow microsphere was proposed involving phase transformation from aluminum hydroxide to laminar boehmite during ageing and a following self-assembling process with NH4Cl as the template during spray drying. The meso-/macro-pores in γ-Al2O3 mainly arise from the stacking of the laminar boehmites which are obtained by ageing the precipitated precursors at 90 °C. NH4Cl, which was the byproduct from the reaction between AlCl3⋅6H2O and NH3⋅H2O, was demonstrated to be an excellent template to act as the core and the barrier for separation of laminar boehmites. No extra NH4Cl was added. The as-synthesized hierarchical porous γ-Al2O3 hollow microsphere presented remarkably higher adsorption capacity, which is thirty times higher adsorption rate for Congo Red than the solid microsphere containing only small mesopores.Graphical abstract

WOx–ZrO2 support was calcined at various temperatures for obtaining controllable activity of copper catalysts for NOx reduction by ammonia. The temperature window of copper catalyst for over 80% NOx conversion shifts from 180–300 to 230–350 °C by elevating the calcination temperature of WOx–ZrO2 support from 500 to 600 °C, due to the increased Brønsted acidity and reduced structure and electronic interactions between copper oxides and tungsten oxides arising from the polymerization of WOx clusters on surface of support. Calcining WOx–ZrO2 support at 700 °C leads to the reduced redox property of copper oxides on the Cu–O–W interface and the formation of bulk-like CuO, results in a low activity of catalyst.Graphical abstractThe temperature window of catalyst for over 80% NOx conversion shifts from 180-300 °C to 230–350 °C by elevating the calcination temperature of WOx–ZrO2 support from 500 °C to 600 °C.Highlights► The temperature window of catalyst is tailored by calcining the support. ► The mechanisms of tailoring the temperature window of catalyst are discussed. ► The polymerization of WOx leads to the increased Brønsted acidity of catalysts. ► The CuOx/WOx interactions are reduced by elevating calcination temperature of support.

Various acidic components (MOx: phosphate, sulfate, tungstate and niobate) were loaded on Ce0.75Zr0.25O2 powders by an impregnation method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol.% H2O to obtain the aged catalysts. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2 programmed-reduction, NH3 adsorption and deNOx activity measurements. The results showed that, among the catalysts investigated, the phosphated Ce0.75Zr0.25O2 catalyst showed the highest hydrothermal stability. The remained high acidity of the phosphated catalyst with moderate redox property helped to maintain the excellent NH3-SCR activity of hydrothermally aged catalyst. Cerium tungstate led to the poor redox property of the tungstated catalyst although the acidity of catalyst was still high. The decomposition of sulfates at temperatures higher than 600 °C restrained the usage of sulfated catalysts in high temperature conditions. The overall dehydration of niobate to niobium oxides led to the low acidity of hydrothermally aged Nb2O5-Ce0.75Zr0.25O2 catalyst.Structure evolution from the fresh catalysts to the hydrothermally aged catalysts