High Activity Of Catalyst Research Articles

Performance of nickel-manganese and nickel-cobalt-manganese mixed oxide catalysts in ethanol total oxidation

The mixed oxide catalysts containing Ni, Co, and Mn components in various molar ratios were examined in the total oxidation of ethanol and the effect of their composition on physical chemical properties and catalytic performance was studied. The catalysts were obtained by calcination (4 h at 500 °C in air) of the coprecipitated precursors. The chemical analysis (AAS), powder XRD, Raman spectroscopy, TEM, N2 adsorption, H2-TPR, and XPS were used for the catalysts characterization. Formation of mixed oxides was indicated by powder XRD and Raman spectroscopy: NiCo2O4 spinel together with NiO were detected in the Ni-Co catalysts, MnIV-containing mixed oxides Ni6MnO8 (murdochite) and NiMnO3 (ilmenite) were identified in the Ni-Mn samples, and Ni-Co-Mn mixed oxides with spinel structure were found in the Ni-Co-Mn catalysts. Combination of transition metal components in the catalysts resulted in a synergistic effect; easier reduction in H2-TPR measurements and enhanced catalytic performance compared to single-component Ni, Co, and Mn oxides were observed. Addition of Mn to the Ni and Ni-Co oxides increased their catalytic activity in the ethanol oxidation, which was higher than that of the Ni-Co catalysts. The Ni-Mn catalyst with Ni:Mn molar ratio of 1:1 showed the highest activity (50 % conversion of ethanol was achieved at 91 °C) and good selectivity (acetaldehyde and carbon monoxide were detected as main byproducts of the ethanol oxidation). High activity of the Ni-Mn catalysts can be ascribed to the presence of MnIV-containing mixed oxides, namely NiMnO3. Activity of the Ni-Co-Mn catalysts, especially those with high (Co+Mn) contents, was comparable with that of the most active Ni-Mn catalyst with Ni:Mn molar ratio of 1:1. The high activity of Ni-Co-Mn catalysts can be explained by the formation of spinel-type mixed oxides with rather poor structure ordering and large surface area.

Controlling the selectivity of the hydrogenolysis of polyamides catalysed by ceria-supported metal nanoparticles

Catalytic hydrogenolysis is a promising approach to transform waste plastic into valuable chemicals. However, the transformation of N-containing polymers, such as polyamides (i.e. nylon), remains under-investigated, particularly by heterogeneous catalysis. Here, we demonstrate the hydrogenolysis of various polyamides catalysed by platinum-group metal nanoparticles supported on CeO2. Ru/CeO2 and Pt/CeO2 are both highly active but display different selectivity; Ru/CeO2 is selective for the conversion of all polyamides into water, ammonia, and methane, whereas Pt/CeO2 yields hydrocarbons retaining the carbon backbone of the parent polyamide. Density functional theory computations illustrate that Pt nanoparticles require higher activation energy for carbon−carbon bond cleavage than Ru nanoparticles, rationalising the observed selectivity. The high activity and product selectivity of both catalysts was maintained when converting real-world polyamide products, such as fishing net. This study provides a mechanistic basis for heterogeneously catalysed polyamide hydrogenolysis, and a new approach to the valorisation of polyamide containing waste.

Development of Highly-Active Catalysts toward Oxygen Reduction by Controlling the Shape and Composition of Pt-Ni Nanocrystals.

Electrocatalysts comprised of Pt-Ni alloy nanocrystals have garnered substantial attention due to their outstanding performance in catalyzing the oxygen reduction reaction (ORR). Herein, we present the synthesis of Pt-Ni nanocrystals with a variety of controlled shapes and compositions in an effort to investigate the impact of the Ni content on the formation of {111} facets and thereby the ORR activity. By completely excluding O2 from the reaction system, we could prevent the generation of Ni(OH)2 on the surface of the nanocrystals and thereby achieve a linear relationship between the atomic ratio of Pt to Ni in the nanocrystals and the feeding ratio of the precursors. The atomic ratio of Pt to Ni in the Pt-Ni nanocrystals was tunable within the range of 1.2-7.2, while their average sizes were kept around 9 nm in terms of edge length. In addition, a quantitative correlation between the area ratio of {111} to {100} facets and the feeding ratio of Pt(II) to Ni(II) was obtained by adjusting the mole fraction of the Ni(II) precursor in the reaction mixture. For the catalysts comprising octahedral nanocrystals, their specific ORR activities exhibited a positive correlation with the Pt/Ni atomic ratio. After the accelerated durability test, both specific and mass activity displayed a volcano-type trend with a peak value at a Pt/Ni atomic ratio of 1.6.

Triggering the high catalytic activity of Ni-based catalyst for urea and urine electrolysis by adding Fe and constructing the CoFeP@Ni3S2 heterostructure

For effective hydrogen production, urea oxidation reaction (UOR) with much lower potential has been used to replace the water oxidation reaction (OER), while fulfilling the wastewater treatment. Development of bifunctional electrocatalysts is the crucial link in urea-assistant water electrolysis. Here, a novel composite consisting of the bimetallic phosphide nanosheets and porous Ni3S2 nanospheres was prepared by a hydrothermal-electrodeposition method. It proves that the NF/CoFeP@Ni3S2 electrode exhibits an outstanding performance for HER/UOR (HER overpotential is 173 mV and EUOR is 1.358 V, 100 mA cm−2). As for a two-electrode system taking NF/CoFeP@Ni3S2 as cathode and anode in urea medium, the voltage at 100 mA cm−2 is just 1.454 V. Even in human urine electrolyte, just only a slight current decrease is observed. Both in urea and urine, the voltage of NF/CoFeP@Ni3S2 remain stable during a 50-hour continuous operation. The formation of heterostructures between the bimetallic phosphides and Ni3S2, and Fe addition realize the gradual improvement in activity from the pristine CoP to CoFeP and then to the CoFeP@Ni3S2. This strategy provides a practical hetero-structured catalyst design form considering the structure properties of urea molecule for the efficient water-hydrogen conversion synchronous sewage treatment.

Non-noble metal high entropy sulfides for efficient oxygen evolution reaction catalysis

Designing high activity and stable oxygen evolution reaction (OER) catalysts is essential for improving the efficiency of the water splitting reaction. The high entropy transition metal sulfide (HES) catalyst will be a promising candidate for accelerating the OER due to its high intrinsic activity and excellent stability. However, the synthesis of HES by chemical methods and the investigation of the structural evolution during the reaction remain a challenging task. In this work, a HES catalyst has been synthesized by a simple thermal injection method. All elements are uniformly distributed in HES nanoparticles, which exhibit excellent activity with an exceptionally low overpotential of 263 at current densities of 100 mA·cm−2 and a low Tafel slope of 51.5 mV·dec−1. This work demonstrates the great potential of HES catalysts as OER electrocatalysts and provides new ideas for the construction and extension of this family of compounds.

The Preparation of Mn-Modified CeO2 Nanosphere Catalysts and Their Catalytic Performance for Soot Combustion

With the increasing stringency of environmental protection regulations, reducing the severe pollution caused by soot particles from diesel vehicle exhaust has become a widespread concern. Catalytic purification technology is currently an efficient method for eliminating soot particles, which needs to develop high-activity catalysts. This work uses a two-step hydrothermal method to synthesize MnOx/CeO2 nanosphere catalysts, which have synergistic effects between manganese and cerium, and have high reactive oxygen species. Among them, the MnCe-1:4 catalyst represents the optimal catalytic activity, and the values of T10, T50, and T90 are 289, 340, and 373 °C, respectively. On account of their simple synthetic procedure and low cost, the prepared MnOx/CeO2 nanosphere catalysts have good prospects for practical applications.

Multifunctional molybdenum-tuning porous nickel-cobalt bimetallic phosphide nanoarrays for efficient water splitting and energy-saving hydrogen production

The sluggish kinetics of the hydrogen evolution reaction (HER) and substantial barriers in the oxygen evolution reaction (OER) significantly impede its application in hydrogen production. To address this issue and enhance energy efficiency in hydrogen generation, we explored a high-activity alkaline HER catalyst while concurrently coupling it with the urea oxidation reaction (UOR). In this work, we designed and synthesized porous molybdenum (Mo)-modulated nickel-cobalt bimetallic phosphide nanoarrays (M0.3NCP@NF). This multifunctional self-supported electrocatalyst demonstrates superior performance in HER, OER, and UOR. The introduction of Mo, in the form of CoMoO4 nanoparticles, promotes interfacial electron transfer to reduce the electron density around the cations in phosphides, enhancing the kinetics and intrinsic activity. Furthermore, the morphological changes induced by Mo accelerate both electron and mass transfer processes. Density functional theory and operando electrochemical impedance spectroscopy indicate that Mo introduction optimizes the interaction with HER intermediate H*, facilitating the conversion to a high-valent active intermediate for OER and accelerating UOR kinetics. Benefiting from dual optimization of morphology and structure, the as-prepared M0.3NCP@NF electrocatalyst demonstrates outstanding HER, OER, and UOR performances. Notably, a full urea electrolysis device powered by M0.3NCP@NF operates with a cell voltage of only 1.53 V to achieve a current density of 100 mA cm−2. which is 240 mV lower than that of conventional water electrolysis, demonstrating the competitive potential of our approach for efficient and energy-saving hydrogen production, along with simultaneous urea wastewater remediation.

Open-Microcolumn Array: A Novel Approach for Enhanced Electrocatalytic Bubble Desorption in Microreactors.

High-efficiency electrocatalytic water splitting requires high intrinsic activity of catalysts and even more importantly favorable mass transfer. However, gas bubbles adhering to the surface of catalysts limit the re-expose of catalytic active sites to the electrolyte and reduce the catalytic activities. The efficient desorption of bubbles can be facilitated by a hierarchical multiscale structure of the electrode surface. Herein, we report an opened periodic three-dimensional electrode composed of iron (Fe)-cobalt (Co)-nickel (Ni) (oxy)hydroxide nanorods (NRs) grown in situ on a high aspect ratio nickel microcolumn array (NCA) for electrocatalytic water splitting. Compared with the flat nickel plate, the NCA not only increases the surface area for catalyst loading but also improves the wettability of the electrolyte on the electrode surface, exhibiting superhydrophilicity/superaerophobicity (the electrolyte and the bubble contact angles were about ∼0 and 163°, respectively), which accelerates the bubble evolution and desorption process. The X-ray photoelectron spectroscopy indicates that the synergy of Fe-Co-Ni could enhance the ratio of Co3+/Co2+ and Ni3+/Ni2+ and promote the electrocatalytic activity. Benefiting from the microstructure design and synergistic effects, the Co4Fe0.5Ni0.5OOH-NR@NCA electrode achieves a superior OER performance with an overpotential of 199 mV at 10 mA·cm-2.

Experimental investigation and 2D mathematical modelling of copper foams packed with Rh-Al2O3 catalysts for the intensification of methane steam reforming

Efficient heat transfer is a crucial factor in the design of compact methane steam reformers for delocalized hydrogen production. The use of copper packed foams was proposed few years ago by our group to strongly intensify heat transfer in these systems, allowing the design of small-scale units with minimal radial temperature gradients. In this study, a new experimental campaign was performed to demonstrate the concept potential under industrially relevant heat fluxes and to establish an experimental foundation for validating a 2D mathematical model of the process. Copper open-cell foams were packed with a Rh/Al2O3 egg-shell catalyst and loaded into a 29.5 mm diameter tubular reactor, which was heated using a lab-scale oven. By leveraging the combined benefits of enhanced heat transfer, granted by the copper foam, and the high activity of the Rh-based eggshell catalyst, experiments were successfully performed at gas hourly space velocities (GHSV) ranging from 10 to 30 Nm3/h/kgcat, with heat duties of up to 9 MW/m3. These experiments lead to a methane conversion close to thermodynamic equilibrium while maintaining limited radial gradients within the system (maximum 20 °C across the mid-radius). A predictive pseudo-heterogeneous 2D reactor model was developed and validated against experimental data. The model accurately captured the observed trends in temperature profiles and outlet concentrations, and can be utilized for optimized design, paving the way for the development of efficient small-scale hydrogen production units.

A clean route of biodiesel production using red mud-based potassium catalyst

In our work, a low-cost and high-efficiency red mud-based potassium composite (KRM) was successfully synthesized via solid-state method using red mud (RM) and potassium carbonate (K2CO3) as material, and then was applied to produce castor oil biodiesel through transesterification. The preparation conditions of red mud-based potassium composite were optimized. The synthesized catalysts were characterized by X-Ray diffractometer (XRD), Scanning electron microscopy (SEM), Hammett method and Brunauer-Emmett-Teller (BET). The maximum conversion from castor oil to biodiesel (94.52%) was acquired with methanol to oil molar ratio 18:1, catalyst dosage 5 wt%, reaction temperature 65 °C and reaction time 2.5 h. According to the thermo-kinetic results, the castor oil transesterification catalyzed by KRM catalyst was a first-order kinetics reaction and was not an exothermic and spontaneous reaction pathway. Particularly, the characterization results indicated that the brightly textural properties (small particle size, high basicity, high surface area and pore volume) were favorable factors for the high catalytic activity of KRM catalyst. The KRM catalyst showed excellent reusability after four cycles. Besides, turnover frequency (TOF), green parameter of transesterification process and cost analysis demonstrated that the transesterification process catalyzed by the high-efficiency KRM catalyst possessed green reaction pathway and the composite catalyst of KRM could effectively reduce the cost of biodiesel production.

Catalysts for hydrogen evolution in universal-pH medium: Construction and structural optimization of Ni3S2/Co9S8/WS2 interface synergies

The performance of heterostructure nanomaterials depends on both the individual components characteristics and the interfaces synergistic effect. In this paper, a high-activity universal-pH HER catalyst, Ti felt supported nanoporous Ni3S2/Co9S8/WS2 (NiCoW-S) is synthesized by electrodeposition and vulcanization. Compared with Ni3S2/Co9S8, Ni3S2/Co9S8/WS2 heterostructure catalyst exhibits enhancement of intrinsic catalytic active center, charge transfer rate and stability in a wide pH range. Benefiting from the 3D porous structure and high-density heterostructure active edge sites, NiCoW-S shows good stability. And Moreover, it only needs 35 and 145 mV to reach 10 mA cm−2 in 0.5 M H2SO4 and 1.0 M KOH, respectively. Based on the experimental analysis, the favorable synergistic effect of metal components and the formation of sulfur vacancies can enhance the conductivity of electron transfer, which promotes electron transfer at the active heterogeneous interface. It provides a reference for designing of advanced metal sulfide heterostructure for hydrogen production in the future.

Magnetic nanoparticles supported copper (II) complex: Fe3O4@DABA-PQ-CuCl2 nanocomposite as an active magnetically recoverable catalyst for preparation of diaryl (aryl-heterocyclic) selenides

ABSTRACT During the last few years, research on new approaches for the synthesis of diaryl selenides containing heterocyclic compounds (Heterocyclic-Selenide-Aryl derivatives) has gained special importance among chemists. These compounds are very valuable from pharmaceutical and pharmacological points of view, and several biological properties such as anti-cancer and antitumor properties have been reported about them. In this research, we presented an ecofriendly and efficient method to prepare diaryl selenides containing heterocyclic compounds through one-pot three-component reactions of heterocyclic compounds with aryl iodides and selenium catalyzed by Fe3O4@DABA-PQ-CuCl2 nanocomposite in PEG as solvent under thermal conditions. Fe3O4@DABA-PQ-CuCl2 nanocomposite was successfully fabricated by using simple method and was fully identified by several spectroscopic techniques. The use of nanocatalysts synthesized in this work has the following advantages over the catalysts reported in the articles: low toxicity, easy storage, transportation, weighing and application, easy preparation of catalyst from cheap and available raw materials, high activity of catalyst due to increased surface area, stability in solvents and at high temperatures, high selectivity, recyclability and reuse of catalyst.

Combination of deep eutectic solvent and functionalized metal-organic frameworks as a green process for the production of 5-hydroxymethylfurfural and furfural from sugars

Biomass is an abundant and sustainable resource that can be converted into energy and chemicals. Therefore, the development of efficient methods for the conversion of biomass into platform intermediates is crucial. In this study, the one-pot conversion of sugars into 5-hydroxymethylfurfural (HMF) and furfural was achieved using the metal–organic framework combined with metal ions [MIL-101(Cr)] as a high-activity catalyst, and a deep eutectic solvent (choline chloride and lactic acid) as a green solvent. The optimal temperature, time, amount of catalyst used, and amount of deep eutectic solvent used were all determined. The highest HMF yield of 49.74% and furfural yield of 55.90% were obtained. The recyclability of the catalysts and deep eutectic solvent was also investigated. After three reaction runs, the HMF yield was still nearly 30.00%. Finally, the MIL-101(Cr) catalytic system was selected to study the kinetic mechanism underlying the conversion of glucose into HMF.

High active and coke-resistant CeNiO3-based catalyst for methane bi-reforming

High active and coke-resistant CeNiO3-based catalyst for methane bi-reforming

Advanced Porous Transport Layers for PEM Water Electrolyzers: Impact of the Interfacial and Bulk Properties of the PTLs on the Electrolyzers Performance

Proton exchange membrane water electrolyzers (PEMWEs) are widely seen as a crucial technology for integration with renewable energy sources to convert the generated electricity to green hydrogen, which is a clean and sustainable energy carrier.1 However, their high capital cost and operational expenditures increase the production cost of green H2.2 To make the technology economically competitive and boost its market penetration, DOE implemented targets of $2 kg-1 by 2025 and $1 kg-1 hydrogen by 2030.3 The interfacial and bulk properties of the porous transport layer (PTL) are vital to the PEMWEs performance.4–6 The optimal bulk properties of PTL improve cell performance mainly by improving the mass transport, while the reduced interfacial contact resistance between the anode catalyst layer and PTL, also enhances the catalyst utilization, allowing for a reduction of the precious metal loading. Further reduction of the interfacial contact resistance between the PTL and the catalyst layer is of crucial importance for increasing the efficiency of the PEMWEs, as well as for decreasing the production cost of green H2.In this study, an innovative reactive spray deposition technology (RSDT) is used to fabricate catalyst-coated membranes (CCMs) and catalyst-coated electrodes (CCEs) with ultra-low PGM loading (0.2 - 0.3 mgPGM cm-2) in both catalyst layers. The RSDT is a flame-based method that combines the synthesis and deposition of the catalyst in a single step, which results in a significant reduction of the MEA fabrication time and cost, respectively.7–9 A set of commercially available Ti PTLs with various thicknesses and porosities have been used to assemble single cells as fabricated MEAs, and their performance has been assessed and compared to the state-of-the-art MEAs for PEMWEs. In addition, the impact of the thickness and porosity of the PTL, as well as the interfacial contact resistance between the PTL and catalyst layer for both single-cell PEMWE configurations (CCMs and CCEs) have been investigated. The performance loss in each cell configuration has been identified and discussed in detail. Furthermore, a standard accelerated stress test (AST) protocol has been applied to assess the durability of the RSDT-fabricated MEAs, with one order of magnitude lower PGM loading in their catalyst layers in comparison to the best reported in the literature MEAs for PEMWEs.Reference1. Carmo, M. et al. A comprehensive review on PEM water electrolysis. Int. J. Hydrogen Energy 38, 4901–4934 (2013).2. Babic, U. et al. Critical Review — Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development Review — Identifying Critical Gaps for Polymer Electrolyte Water. (2017) doi:10.1149/2.1441704jes.3. https://www.energy.gov/eere/fuelcells/hydrogen-shot4. Peng, X. et al. Insights into Interfacial and Bulk Transport Phenomena Affecting Proton Exchange Membrane Water Electrolyzer Performance at Ultra-Low Iridium Loadings. Adv. Sci. 8, 1–9 (2021).5. Bühler, M. et al. Optimization of anodic porous transport electrodes for proton exchange membrane water electrolyzers. J. Mater. Chem. A 7, 26984–26995 (2019).6. Kulkarni, D. et al. Elucidating effects of catalyst loadings and porous transport layer morphologies on the operation of proton exchange membrane water electrolyzers. Appl. Catal. B Environ. 308, 121213 (2022).7. Zeng, Z. et al. Degradation Mechanisms in Advanced MEAs for PEM Water Electrolyzers Fabricated by Reactive Spray Deposition Technology. J. Electrochem. Soc. 169, 054536 (2022).8. Mirshekari, G. et al. High-performance and cost-effective membrane electrode assemblies for advanced proton exchange membrane water electrolyzers: Long-term durability assessment. Int. J. Hydrogen Energy 46, 1526–1539 (2021).9. Yu, H. et al. Nano-size IrOx catalyst of high activity and stability in PEM water electrolyzer with ultra-low iridium loading. Appl. Catal. B Environ. 239, 133–146 (2018).

Nickel-constructing interfaces of multiheterostructure on self-supporting electrode for efficient overall urea-water splitting

Water splitting is an environmentally friendly strategy for producing hydrogen but is constrained by the high theoretical potential of the oxygen evolution reaction (OER) at the anode. It is possible to save energy by substituting the OER with the urea oxidation reaction (UOR) with a low theoretical potential. In particular, developing bifunctional catalysts (hydrogen evolution reactions (HER)/UOR) and exploring their catalytic mechanisms and active sites are highly desirable with the rapid development of the hydrogen economy. Herein, the combination of electrodeposition and immersion methods to grow a well-aligned MOF on a graphene-like material (MXene) is reported. Specifically, Ni3S2 species were formed on the hexahedral structure of cobalt-based MOF (CoMOF) by electrodeposition. The resultant M/CM/Ni3S2/NF demonstrates good electrocatalytic capabilities toward the HER and UOR, with overpotentials and potentials of 0.174 and 1.392 V required to reach 100 mA cm−2, respectively. DFT results established that the coupling of MXene, CoMOF, and Ni3S2 can optimize the free energy of hydrogen adsorption on the catalyst surface. Furthermore, in situ XRD revealed that the (111), (2¯ 11) and (220) crystal planes resulted in good stability of the material. This work provides an innovative and novel route for designing high-activity bifunctional catalysts for various electrochemical energy applications.

Efficient hydrogen production from formic acid over Ag@AgPd nanotriangulars at room temperature

Hydrogen with advantages of high energy density, zero pollution and zero carbon dioxide emissions is regarded as a carrier of clean energy for replacing fossil fuels. Therefore, the development of a high activity, selectivity and stability catalyst for H2 production remains a great challenge. Herein, we report a new Ag@AgPdx nanotriangulars catalysts via immobilizing Pd atoms onto the surface of Ag nanotriangulars, for H2 production from formic acid (FA) at room temperature, with superior catalytic activity and stability over commercial Pd/C and Pt/C. The in-situ DRIFT results shown the FA dehydrogenation process over Ag@AgPd0.8 nanotriangulars, first the HCOOH* was rapidly converted to HCOO*, and finally to CO2*, which explained the fact that Ag@AgPd0.8 nanotriangulars have high activity and selectivity for FA dehydrogenation. This strategy opens up a new way to design effective catalysts for efficient H2 production from FA dehydrogenation to meet the requirement and applications of fuel cell.

Synergetic influence of nitrogen-doped species and hollow microporous structure on surface active sites of carbonaceous catalysts for oxygen reduction reaction of Zn-air battery

The development of metal-free carbon catalysts towards oxygen reduction reaction has focused on their surface active sites multiplied by heteroatom doping and/or pore adjustment. Herein, to coordinate nitrogen doping and pore structure is uncovered to expect highly comparable properties of the carbons to those of commercial Pt/C catalysts. N-doped porous carbons have been fabricated by a ready and collaborative strategy in two-step pyrolysis. The first is to pyrolyze only a raw citrate forming porous carbons with micro-, meso-, or macro-porous structure. Subsequent cyanoguanidine thermolysis induces gaseous nitrogen doping to generate edge defects. Especially, the hollow microporous architecture gives rise to large specific surface area and relatively high catalytic activity of the carbon catalysts (denoted as N-CK). Furthermore, theoretical calculations indicate meta-positional dual-N doped sites with the carbon combining graphitic N and pyridinic N (Gn-C-Py) show a minimum overpotential of 0.39 V. Such a catalyst under the synergistic effect of high-active N-doped species and hollow microporous architecture enables its Zn-air batteries to deliver a superior peak power density of 99.9 mW cm−2 vs. 95.7 mW cm−2 for those using commercial Pt/C. Considering the comprehensive comparability, the N-CK catalysts in a hollow microporous construction possess great feasibility for practical applications.

Enabling High Activity Catalyst Co3O4@CeO2 for Propane Catalytic Oxidation via Inverse Loading.

Propane catalytic oxidation is an important industrial chemical process. However, poor activity is frequently observed for stable C-H bonds, especially for non-noble catalysts in low temperature. Herein, we reported a controlled synthesis of catalyst Co3O4@CeO2-IE via inverse loading and proposed a strategy of oxygen vacancy for its high catalytic oxidation activity, achieving better performance than traditional supported catalyst Co3O4/CeO2-IM, i.e., the T50 (temperature at 50% propane conversion) of 217 °C vs. 235 °C and T90 (temperature at 90% propane conversion) of 268 °C vs. 348 °C at the propane space velocity of 60,000 mL g-1 h-1. Further investigations indicate that there are more enriched oxygen vacancies in Co3O4@CeO2-IE due to the unique preparation method. This work provides an element doping strategy to effectively boost the propane catalytic oxidation performance as well as a bright outlook for efficient environmental catalysts.

Highly Active NiO-Ni(OH)2 -Cr2 O3 /Ni Hydrogen Evolution Electrocatalyst through Synergistic Reaction Kinetics.

High activity catalysts for hydrogen evolution reaction (HER) play a key role in converting renewable electricity to storable hydrogen fuel. Great effort has been devoted to the search for noble metal free catalysts to make electrolysis viable for practical applications. Here, a non-precious metal oxide/metal catalyst with high intrinsic activity comparable to Pt/C was reported. The electrocatalyst consisting of NiO, Ni(OH)2 , Cr2 O3 , and Ni metal exhibits a low overpotential of 27, 103, and 153 mV at current densities of 10, 100, and 200 mA cm-2 , respectively, in a 1.0 m NaOH electrolyte. The activity is much higher than that of NiOx /Ni or Cr2 O3 alone, showing the synergistic effect of NiOx /Ni and Cr2 O3 on catalyzing HER. Density functional theory calculations shows that NiO and Cr2 O3 on Ni surface lower the disassociation energy barrier for breaking H-OH bond, while Ni(OH)2 and Cr2 O3 create preferred sites on Ni surface with near-zero H* adsorption free energy to promote H* to gaseous H2 evolution. These synergistic effects of multiple-oxides/metal composition enhance the disassociation of H-OH and the evolution of H* to gaseous H2 , thus achieving high activity and demonstrating a promising composition design for noble metal free catalyst.