Boosted Light Alkane Deep Oxidation via Metal Bond Length Modulation-Induced C-C Bond Preferential Activation.

Light alkanes (LAs), typical VOCs existing in both stationary and mobile sources, pose significant environmental concerns. Although noble metal catalysts demonstrate strong C-H bond activation, their effectiveness in degrading LAs is hindered by inherent challenges, including poor chemical stability and water resistance. Here, from a new perspective, we propose a feasible strategy that adjusting the metal bond lengths within Pd clusters through partial substitution of smaller radius 3d transition metals (3dTMs) to prioritize the activation of low-energy C-C bonds within LAs. Benefiting from this, PdCo/CeO2 exhibits exceptional catalytic performance in propane degradation due to their high capacity for C-C cleavage stemming from the shorter Pd-Co length (2.51 Å) and lower coordination number (1.73), boosting the activation of α-H and ß-H of propane simultaneously and accelerating the mobility of postactivated oxygen species to prevent Pd center deep oxidation. The presence of 3dTMs on Pd clusters improves the redox and charge transfer ability of catalysts, resulting in an amplified generation of oxygen vacancies and facilitating the adsorption and activation of reactants. Mechanistic studies and DFT calculations suggest that the substitution of 3dTMs significantly accelerate C-C bond cleavage within C3 intermediates to generate the subsequent C2 and C1 intermediates, suppressing the generation of harmful byproducts.

Creating Frustrated Lewis Pairs in Defective Boron Carbon Nitride for Electrocatalytic Nitrogen Reduction to Ammonia.

The electrocatalytic nitrogen reduction reaction (NRR) on metal-free catalysts is an attractive alternative to the industrial Haber-Bosch process. However, the state-of-the-art metal-free electrocatalysts still suffer from low Faraday efficiencies and low ammonia yields. Herein, we present a molecular design strategy to develop a defective boron carbon nitride (BCN) catalyst with the abundant unsaturated B and N atoms as Lewis acid and base sites, which upgrades the catalyst from a single "Lewis acid catalysis" to "frustrated Lewis pairs (FLPs) catalysis." 14 N2 /15 N2 exchange experiments and density functional theory (DFT) calculations reveal that FLPs can adsorb an N2 molecule to form a six-membered ring intermediate, which enables the cleavage of N2 via a pull-pull effect, thereby significantly reducing the energy barrier to -0.28 eV. Impressively, BCN achieves a high Faraday efficiency of 18.9 %, an ammonia yield of 20.9 µg h-1 mg-1 cat. , and long-term durability.

Modulating the Electronic Metal-Support Interactions in Single-Atom Pt1 -CuO Catalyst for Boosting Acetone Oxidation.

The development of highly active single-atom catalysts (SACs) and identifying their intrinsic active sites in oxidizing industrial hazardous hydrocarbons are challenging prospects. Tuning the electronic metal-support interactions (EMSIs) is valid for modulating the catalytic performance of SACs. We propose that the modulation of the EMSIs in a Pt1 -CuO SAC significantly promotes the activity of the catalyst in acetone oxidation. The EMSIs promote charge redistribution through the unified Pt-O-Cu moieties, which modulates the d-band structure of atomic Pt sites, and strengthens the adsorption and activation of reactants. The positively charged Pt atoms are superior for activating acetone at low temperatures, and the stretched Cu-O bonds facilitate the activation of lattice oxygen atoms to participate in subsequent oxidation. We believe that this work will guide researchers to engineer efficient SACs for application in hydrocarbon oxidation reactions.

Structure engineering of CeO2 for boosting the Au/CeO2 nanocatalyst in the green and selective hydrogenation of nitrobenzene.

Exploring eco-friendly and cost-effective strategies for structure engineering at the nanoscale is important for boosting heterogeneous catalysis but still under a long-standing challenge. Herein, multifunctional polyphenol tannic acid, a low-cost natural biomass containing catechol and galloyl species, was employed as a green reducing agent, chelating agent, and stabilizer to prepare Au nanoparticles, which were dispersed on different-shaped CeO2 supports (e.g., rod, flower, cube, and octahedral). Systematic characterizations revealed that Au/CeO2-rod had the highest oxygen vacancy density and Ce(III) proportion, favoring the dispersion and stabilization of the metal active sites. Using isopropanol as a hydrogen-transfer reagent, deep insights into the structure-activity relationship of the Au/CeO2 catalysts with various morphologies of CeO2 in the catalytic nitrobenzene transfer hydrogenation reaction were gained. Notably, the catalytic performance followed the order: Au/CeO2-rod (110), (100), (111) > Au/CeO2-flower (100), (111) > Au/CeO2-cube (100) > Au/CeO2-octa (111). Au/CeO2-rod displayed the highest conversion of 100% nitrobenzene and excellent stability under optimal conditions. Moreover, DFT calculations indicated that nitrobenzene molecules had a suitable adsorption energy and better isopropanol dehydrogenation capacity on the Au/CeO2 (110) surface. A reaction pathway and the synergistic catalytic mechanism for catalytic nitrobenzene transfer hydrogenation are proposed based on the results. This work demonstrates that CeO2 structure engineering is an efficient strategy for fabricating advanced and environmentally benign materials for nitrobenzene hydrogenation.

The influence of doping amount on the catalytic oxidation of formaldehyde by Mn-CeO2 mixed oxide catalyst: A combination of DFT and microkinetic study.

Formaldehyde (HCHO) is a major environmental pollutant. The Mn-doped CeO2 catalyst has good catalytic performance for the oxidation of HCHO. The catalytic activity can be effectively tuned by changing the amount of metal doping. In this paper, density functional theory combined with micro-kinetic analysis are employed to provide a molecular level understanding to such effects. The CeO2(111) surface with different Mn doping content was used to study the oxidation mechanism of HCHO. Highly dispersed Mn doped ceria was dominant at low content of Mn. While with the increase of Mn doping, Mn begins to accumulate on the CeO2(111) surface. It is not conducive to the breaking of C-H bonds, the generation of oxygen vacancies and the adsorption of active oxygen species. Therefore, the low-content Mn-doped CeO2 catalyst has higher catalytic oxidation activity of HCHO. The present contribution is useful for further optimization of Mn-CeO2 catalysts towards HCHO oxidation.

Nickel-Iron Nitride-Nickel Sulfide Composites for Oxygen Evolution Electrocatalysis.

Advance applications like water splitting system and rechargeable metal-air battery are highly dependent on efficient electrocatalyst for the oxygen evolution reaction (OER). Heterostructured materials, with a high active surface area and electron effect, accomplish enhanced catalytic performance. Here, a nitride-sulfide composite (FeNi3N-Ni3S2) has been prepared by a simple hydrothermal process coupled with nitridation. The prepared composite electrocatalyst FeNi3N-Ni3S2 possesses lower electron densities compared to those of FeNi3N and Ni3S2, lessening the activation energy (Ea) toward the OER. Consequently, the prepared FeNi3N-Ni3S2 exhibits excellent OER performance with a low overpotential (230 mV) and a small Tafel slope (38 mV dec-1). Highly stable FeNi3N-Ni3S2 composite delivers lower charging voltage and extended lifetime in rechargeable Zn-air battery, compared with IrO2.

Defective Mn xZr1- xO2 Solid Solution for the Catalytic Oxidation of Toluene: Insights into the Oxygen Vacancy Contribution.

Oxygen vacancy is conducive to molecular oxygen adsorption and activation, and it is necessary to estimate its contribution on catalysts, especially the doped system for volatile organic compound (VOC) oxidation. Herein, a series of doped Mn xZr1- xO2 catalysts with oxygen vacancy were prepared by partially substituting Zr4+ in a zirconia with low-valent manganese (Mn2+). Compared with the corresponding mechanically mixed samples (MB-x) without oxygen vacancy, Mn xZr1- xO2 catalysts exhibited better toluene conversion and specific reaction rate, where the differential values were calculated to estimate the contribution of oxygen vacancy on catalytic performance. The increase in oxygen vacancy concentrations in Mn xZr1- xO2 catalysts can boost the differential values, implying the enhancement of oxygen vacancy contribution. Density functional theory (DFT) calculations further confirmed the contribution of oxygen vacancy, and molecular oxygen is strongly absorbed and activated on a defective Mn-doped c-ZrO2 (111) surface with oxygen vacancy rather than a perfect m-ZrO2 (-111) surface or a perfect Mn-doped c-ZrO2 (111) surface, thus resulting in the significant improvement in catalytic activity for toluene oxidation. In situ DRIFTS spectra revealed that the oxygen vacancy can alter the toluene degradation pathway and accelerate the intermediates to convert into CO2 and H2O, thus leading to a low activation energy and high specific reaction rate.