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Pt/C and SO42−/ZrO2 were mechanically mixed as the catalysts for p-aminophenol synthesis by catalytic transfer hydrogenation of nitrobenzene in water with formic acid as the hydrogen source. The effect of Pt loading and the solid acid on the reaction was investigated. PAP selectivity reached a maximum at a loading of 1 wt%. The characterization results revealed the presence of three valence states of Pt. Pt0 was beneficial for the nitrobenzene hydrogenation, while higher valence Pt contributed to the formic acid decomposition. The catalytic performance of different solid acid catalysts, including HZSM-5, Hβ, SO42−/ZrO2 and SO42−/TiO2, was compared. It was found that Lewis acid sites with strong acid strength were favorable for p-aminophenol formation, and SO42−/ZrO2 showed higher catalytic activity for the reaction. Using Pt/C + SO42−/ZrO2 as the catalyst, the reaction conditions were optimized. Under the optimal reaction conditions, the nitrobenzene conversion and the p-aminophenol selectivity were 80.0% and 47.6%, respectively. The reaction mechanism was also proposed based on the main by-products of the reaction. [ABSTRACT FROM AUTHOR]

Highly active Keggin-type silicotungstic acid (SiW12) with oxygen vacancy (Ov) defects was encapsulated into the magnetic floral N-doped carbon microspheres (γ-Fe2O3@NC-300) through the facile one-step air pyrolysis of the precursor comprising core–shell Fe3O4@polydopamine (Fe3O4@PDA) and SiW12 to prepare γ-Fe2O3@NC@SiW12-300. The fabricated catalysts were systematically characterized and subsequently employed for the oxidation desulfurization (ODS) of the model fuel. The magnetic floral γ-Fe2O3@NC@SiW12-300 catalyst exhibited nearly perfect catalytic activity, which under mild conditions could remove 100% amount of 4000 ppm DBT in model fuel within 20 min (0.03 g catalysts and n(H2O2)/n(S) of 2). The catalyst activity is mainly attributed to the high activity SiW12 with the Ov defect and its outstanding dispersibility in γ-Fe2O3@NC, along with the high number of exposed active sites. A selected catalyst, γ-Fe2O3@NC@SiW12-300, showed a noticeable turnover frequency (TOF) (110.07 h−1) and lower activation energy (38.79 kJ mol−1) in oxidative desulfurization (ODS) with good recyclability. HO˙ radical was found to be the active species involved in ODS as confirmed by the EPR and scavenger experiments. Additionally, the fabricated catalyst can be conveniently separated and recycled within an externally applied magnetic field. [ABSTRACT FROM AUTHOR]

The urea oxidation reaction (UOR), which possesses a low theoretical potential and superior kinetics, is an attractive substitute for the anodic oxygen evolution reaction (OER) in overall water splitting; however, the implementation of hydrogen production in overall urea splitting is impeded by the deficiency of highly efficient, durable and cost-effective catalysts. Herein, we fabricated an Ni2P–MoP2 heterostructure with a hierarchical structure grown on carbon paper (Ni–Mo–P/CP), which exhibited robust activity and outstanding durability for the electrocatalytic oxidation of urea. The Ni–Mo–P/CP catalyst possessed an ultralow potential of 1.39 V to obtain the current density of 100 mA cm−2, small Tafel slope (27 mV dec−1) and long-term durability with almost no decay within 15 h. The experimental characterization revealed that the optimized electronic structure and the synergistic effect of abundant exposed active sites in the Ni–Mo–P/CP catalyst contribute to the efficient UOR catalytic activity. This work enriches the candidate catalysts for the UOR and promotes the industrial development of hydrogen production. [ABSTRACT FROM AUTHOR]

High activity hyper-crosslinked polymer solid acids (HCPSAs) were prepared from different aromatic monomers, and the structure was regulated by selecting the type and size of aromatic monomers. The results indicated that aromatic monomers affect not only the skeleton structure of HCPSAs, but also the loading of active groups significantly. The structural change of HCPSAs displayed a certain regularity as the size of the aromatic monomer increased; however, the catalytic activity of HCPSAs in oleic acid methylation and cellulose hydrolysis exhibited a different trend. HCPSA derived from thiophene presented the highest oleic acid conversion, while HCPSA prepared from phenanthrene showed the highest reducing sugar yield. The highly active HCPSA for a specific reaction can be obtained by controlling aromatic monomers. [ABSTRACT FROM AUTHOR]

Microwave assisted lignin depolymerization was investigated over HSZ-supported CuNiAl-based catalysts. The synergistic effect between the acidic HSZ support and mixed metal oxides was studied in detail to explore the difference in catalytic activity during the lignin depolymerization process. Improvements in bio-oil properties, such as the H/C ratio and HHV value, were observed in comparison with raw lignin under rather mild conditions (140 °C, 80 min) in the absence of external hydrogen. The molecular weight of bio-oil obtained over HSZ-supported catalysts decreased, indicating that the increased acidity in the catalyst could facilitate microwave assisted lignin depolymerization. The product distributions in bio-oil were also analyzed and plausible depolymerization mechanisms were proposed considering the distributions of lignin-derived dimers/trimers and monomers. [ABSTRACT FROM AUTHOR]

Co, N co-doped carbon (CoN@C) with properly engineered heteropores was facilely synthesized using metal carbonate hydroxides as metal precursor and multistage porogen. CoN@C therefore exhibits superior ORR catalytic activity with a half-wave potential of 0.876 V vs. RHE, and the CoN@C-based zinc-air battery can be stably cycled for 100 h. [ABSTRACT FROM AUTHOR]

Although carbon nanomaterials show good potential as efficient electrocatalysts for oxygen reduction reaction (ORR), their inferior long-term stability due to their high surface energy resulting in compact restacking limits their practical performance. To overcome this issue, here, we design and construct an anti-agglomerating single-walled carbon nanotube (SWNT) catalyst by using poly-3,4-ethylenedioxythiophene (PEDOT) as an upholder. Physical characteristic results indicate that PEDOT effectively fills in the interweaved zone or adheres to the SWNT surface. Furthermore, S atoms can be doped into the lattice and produce more defects. Electrochemical tests show that SWNTs@PEDOT exhibits similar catalytic activities towards ORR to SWNTs, and both of them can realize a quasi-4e ORR pathway. Within a 32 000 s long-term test, the cathodic current of the SWNTs toward ORR gradually decays to 58% of the initial value; in contrast, SWNTs@PEDOT shows excellent stability with several stages of rise, fall, rise to 105% of the initial current. The excellent stability is due to the stable skeleton caused by PEDOT preventing agglomeration of SWNTs. The equilibrium of swelling and shrinkage of PEDOT even lead to an increase and favorable stability of the current. This suggests a practical method to overcome the weakness of agglomeration, thus enhancing the long-term stability for nano-carbon catalysts. [ABSTRACT FROM AUTHOR]

Herein, CO oxidation on Ni-doped graphene (Ni-Gr) is investigated by first-principle calculations. The strong binding energy (−7.57 eV) of the Ni atom at a single vacancy in graphene and high energy barrier (3.41 eV) for Ni atom mobility in graphene suggest that graphene is stable even after Ni doping, which avoids the problem of metal clustering. The stronger binding interaction between Ni-Gr and O2 than that between Ni-Gr and CO can prevent CO poisoning to Ni-Gr. To explore the catalytic effect of CO oxidation on Ni-Gr, both the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms are investigated. The overall energy barrier at 0 K for the LH and ER mechanisms is 0.63 and 0.77 eV, respectively. At 298.15 K, the overall energy barrier for the LH mechanism decreases to 0.58 eV, whereas that for the ER mechanism increases to 0.88 eV, which implies that CO oxidation on Ni-Gr prefers to proceed via the LH mechanism kinetically. Our results show that the studied system, Ni-Gr, has chemical stability against metal clustering and CO poisoning, and it is a promising catalyst for CO oxidation at mild temperatures. This study provides a good theoretical guideline for the development of Ni-Gr based CO oxidation catalysts. [ABSTRACT FROM AUTHOR]