New insight into the design of highly dispersed Pt supported CeO_(2)-TiO_(2) catalysts with superior activity for VOCs low-temperature removal

A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.

β-Cyclodextrin polymer networks stabilized gold nanoparticle with superior catalytic activities

Support materials play a significant role in heterogeneous nanocatalysis.In this work,β-cyclodextrin(β-CD)was used directly as a monomer to construct polymer networks for gold nanoparticles(Au NPs)immobilization.Using the simple nucleophilic substitution reaction,β-CD based polymer networks(β-CDP-N andβ-CDP-C)were successfully prepared.Compared toβ-CDP-C,the hydroxyl groups and N atoms inβ-CDP-N played a synergistic role in immobilizing smaller Au NPs,thus leading to high catalytic activities.Notably,the apparent rate constant(Kapp)value for Au@β-CDP-N in the reduction of 4-nitrophenol to 4-aminophenol is 14.15×10^(-2)s^(-1),which shows a significant improvement over all previously reported Au NPs with solid supports under similar conditions.Considering the negligible porosity of theβ-CDP-N support,we purposed a"capture-catalysis-release"model to explain the high catalytic activity of Au@β-CDP-N.This explanation is supported by the guest-responsive properties ofβ-CDP-N.Moreover,the Au@β-CDP-N is easily recycled and maintained its high catalytic efficiency after seven successful cycles.

Synergistic effects of 1T MoS_(2)and interface engineering on hollow NiCoP nanorods for enhanced hydrogen evolution activity

Metallic 1T-phase molybdenum disulfide(1T-MoS_(2))shows more excellent electrocatalytic performance for hydrogen evolution reaction(HER)than semiconducting 2H-phase MoS_(2)(2H-MoS_(2)).Therefore,the facile controllable synthesis of hierarchical structure with rich 1T-MoS_(2)is desired for highly efficient electrocatalytic performance.In this work,a simple solvothermal method is proposed to fabricate hol-low NiCoP/MoS_(2)-V heterostructure with 63.2%1T-MoS_(2),in which the abundant catalytic active sites are exposed,the mass transfer properties are improved,and the electronic states are optimized.Moreover,the low energy difference between 2H and 1T phases and near zero free energy of hydrogen adsorption(△G H∗)result in fast kinetics and excellent catalytic performances.Specifically,the NiCoP/MoS_(2)-V com-posite exhibits enhanced HER activity with a low overpotential of 74.6 mV at 10 mA cm^(-2)and superior stability in alkaline electrolytes.This efficient design opens up new vistas for developing high-activity electrocatalysts.

Hierarchical coral-like NiMoS nanohybrids as highly efficient bifunctional electrocatalysts for overall urea electrolysis

Novel hierarchical coral-like Ni-Mo sulfides on Ti mesh （denoted as HC-NiMoSfri） were synthesized through facile hydrothermal and subsequent sulfuration processes without any template. These non-precious HC-NiMoS/Ti hybrids were explored as bifunctional catalysts for urea-based overall water splitting, including the anodic urea oxygen evolution reaction （UOR） and cathodic hydrogen evolution reaction （HER）. Due to the highly exposed active sites, excellent charge transfer ability, and good synergistic effects from multi-component reactions, the HC-NiMoS/Ti hybrid exhibited superior activity and high stability, and only a cell voltage of 1.59 V was required to deliver 10 mA.cm-2 current density in an electrolyte of 1.0 M KOH with 0.5 M urea.

Nickel-carbonate nanowire array： An efficient and durable electrocatalyst for water oxidation under nearly neutral conditions

It is highly attractive but still remains a great challenge to develop an efficient electrocatalyst for oxygen evolution reaction under nearly neutral conditions. In this work, we report the transformation of Ni3S2 nanowire array on nickel foam into the amorphous nickel carbonate nanowire array on nickel foam （NiCO3/NF）. The resulting NiCO3/NF shows high electrocatalytic activity towards water oxidation and affords current density of 50 mA. cm-2 at overpotential of 395 mV in 1.0 mol·L^-1 KHCO3. Moreover, this NiCO3/NF is also durable with a long-term electrochemical durability of 60 h. This catalyst electrode achieves a high turnover frequency of 0.21 mol O2·s^-1 at the overpotential of 500 mV.