Opening catalytic sites in the copper-triazoles framework via defect chemistry for switching on the proton reduction

Close proximity between different catalytic sites is crucial for accelerating or even enabling many important catalytic reactions. Photooxidation and photoreduction in photocatalysis are generally separated from each other, which arises from the hole–electron separation on photocatalyst surface. Here, we show with widely studied photocatalyst Pt/TiO2 as a model, that concentrating abundant oxygen vacancies only at the metal–oxide interface can locate hole-driven oxidation sites in proximity to electron-driven reduction sites for triggering unusual reactions. Solar hydrogen production from aqueous-phase alcohols, whose hydrogen yield per photon is theoretically limited below 0.5 through conventional reactions, achieves an ultrahigh hydrogen yield per photon of 1.28 through the unusual reactions. We demonstrated that such defect engineering enables hole-driven CO oxidation at the Pt-TiO2 interface to occur, which opens up room-temperature alcohol decomposition on Pt nanoparticles to H2 and adsorbed CO, accompanying with electron-driven proton reduction on Pt to H2.

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Dislocations, Ordering and Antiferromagnetic Domains in MnO

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069600 ◽

1970 ◽

Vol 28 ◽

pp. 522-523

Author(s):

D. J. Barber ◽

R. G. Evans

Keyword(s):

Electron Diffraction ◽

Single Crystal ◽

Optical Microscopy ◽

Defect Chemistry ◽

Magnetic Structures ◽

Optically Transparent ◽

Magnetic Features ◽

Antiferromagnetic Domains

Manganese (II) oxide, MnO, in common with CoO, NiO and FeO, possesses the NaCl structure and shows antiferromagnetism below its Neel point, Tn∼ 122 K. However, the defect chemistry of the four oxides is different and the magnetic structures are not identical. The non-stoichiometry in MnO2 small (∼2%) and below the Tn the spins lie in (111) planes. Previous work reported observations of magnetic features in CoO and NiO. The aim of our work was to find explanations for certain resonance results on antiferromagnetic MnO.Foils of single crystal MnO were prepared from shaped discs by dissolution in a mixture of HCl and HNO3. Optical microscopy revealed that the etch-pitted foils contained cruciform-shaped precipitates, often thick and proud of the surface but red-colored when optically transparent (MnO is green). Electron diffraction and probe microanalysis indicated that the precipitates were Mn2O3, in contrast with recent findings of Co3O4 in CoO.

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Synthesis of HTCMgFe for the degradation of indigo carmine through heterogeneous photo-Fenton treatment

MRS Advances ◽

10.1557/adv.2020.421 ◽

2020 ◽

Vol 5 (62) ◽

pp. 3273-3282

Author(s):

I. Cosme-Torres ◽

M.G. Macedo-Miranda ◽

S.M. Martinez-Gallegos ◽

J.C. González-Juárez ◽

G. Roa-Morales ◽

...

Keyword(s):

Electron Microscopy ◽

Treatment Time ◽

Uv Light ◽

Indigo Carmine ◽

Oh Radicals ◽

Absorption Bands ◽

Chromophore Group ◽

X Ray ◽

Catalytic Sites ◽

Scanning Electron

AbstractThe heterogeneous catalyst HTCMgFe was used in the degradation of the IC, through the heterogeneous photo-fenton treatment, this material in combination with H2O2 and UV light degraded the dye in 30 min at pH 3. As the amount of HTCMgFe increases the degradation it was accelerated because there are more active catalytic sites of Fe2+ on the surface of the material, which generates a greater amount of •OH radicals. The HTCMgFe was characterized by infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray energy dispersive elemental analysis (EDS). The UV-vis spectrum shows that the absorption bands belonging to the chromophore group of the IC disappear as the treatment time passes, indicating the degradation of the dye.

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An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

10.26434/chemrxiv.12159207.v1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Peter T. Smith ◽

Sophia Weng ◽

Christopher Chang

Keyword(s):

Proton Transfer ◽

Co2 Reduction ◽

Iron Porphyrin ◽

Redox Mediators ◽

Reservoir Properties ◽

Proton Reduction ◽

Electrochemical Co2 Reduction ◽

Starting Point ◽

Rate Improvement ◽

Molecular Catalysts

We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO2 to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO2 versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO2 reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

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Nanometer Scale Spectroscopic Visualization of Catalytic Sites During a Hydrogenation Reaction on a Pd/Au Bimetallic Catalyst

10.26434/chemrxiv.12346823.v3 ◽

2020 ◽

Author(s):

hao yin ◽

Liqing Zheng ◽

Wei Fang ◽

Yin-Hung Lai ◽

Nikolaus Porenta ◽

...

Keyword(s):

Catalytic Hydrogenation ◽

Density Functional ◽

Hydrogen Transfer ◽

Bimetallic Catalyst ◽

Local Environment ◽

Hydrogenation Reaction ◽

Boundary Density ◽

Catalytic Sites ◽

Powerful Analytical Tool ◽

Tip Enhanced Raman Spectroscopy

Understanding the mechanism of catalytic hydrogenation at the local environment requires chemical and topographic information involving catalytic sites, active hydrogen species and their spatial distribution. Here, tip-enhanced Raman spectroscopy (TERS) was employed to study the catalytic hydrogenation of chloro-nitrobenzenethiol on a well-defined Pd(sub-monolayer)/Au(111) bimetallic catalyst (pH2=1.5 bar, 298 K), where the surface topography and chemical fingerprint information were simultaneously mapped with nanoscale resolution (≈10 nm). TERS imaging of the surface after catalytic hydrogenation confirms that the reaction occurs beyond the location of Pd sites. The results demonstrate that hydrogen spillover accelerates hydrogenation at the Au sites within 20 nm from the bimetallic Pd/Au boundary. Density functional theory was used to elucidate the thermodynamics of interfacial hydrogen transfer. We demonstrate that TERS as a powerful analytical tool provides a unique approach to spatially investigate the local structure-reactivity relationship in catalysis.

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Nanometer Scale Spectroscopic Visualization of Catalytic Sites During a Hydrogenation Reaction on a Pd/Au Bimetallic Catalyst

10.26434/chemrxiv.12346823.v1 ◽

2020 ◽

Author(s):

Hao Yin ◽

Liqing Zheng ◽

Wei Fang ◽

Yin-Hung Lai ◽

Nikolaus Porenta ◽

...

Keyword(s):

Catalytic Hydrogenation ◽

Density Functional ◽

Hydrogen Transfer ◽

Bimetallic Catalyst ◽

Local Environment ◽

Hydrogenation Reaction ◽

Boundary Density ◽

Catalytic Sites ◽

Powerful Analytical Tool ◽

Tip Enhanced Raman Spectroscopy

Understanding the mechanism of catalytic hydrogenation at the local environment requires chemical and topographic information involving catalytic sites, active hydrogen species and their spatial distribution. Here, tip-enhanced Raman spectroscopy (TERS) was employed to study the catalytic hydrogenation of chloro-nitrobenzenethiol on a well-defined Pd(sub-monolayer)/Au(111) bimetallic catalyst (pH2=1.5 bar, 298 K), where the surface topography and chemical fingerprint information were simultaneously mapped with nanoscale resolution (≈10 nm). TERS imaging of the surface after catalytic hydrogenation confirms that the reaction occurs beyond the location of Pd sites. The results demonstrate that hydrogen spillover accelerates hydrogenation at the Au sites within 20 nm from the bimetallic Pd/Au boundary. Density functional theory was used to elucidate the thermodynamics of interfacial hydrogen transfer. We demonstrate that TERS as a powerful analytical tool provides a unique approach to spatially investigate the local structure-reactivity relationship in catalysis.

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Dissolution and Performing Homogeneous Photocatalysis of Polymeric Carbon Nitride

10.26434/chemrxiv.6959627 ◽

2018 ◽

Author(s):

Chaofeng Huang ◽

Jing Wen ◽

Yanfei Shen ◽

Fei He ◽

Li Mi ◽

...

Keyword(s):

Conjugated Polymer ◽

Carbon Nitride ◽

Heterogeneous Catalysts ◽

Methane Sulfonic Acid ◽

Environment Friendly ◽

The Poor ◽

Catalytic Sites ◽

Homogeneous Photocatalysis ◽

Polymeric Carbon ◽

First Time

<a></a><a>As a metal-free conjugated polymer, carbon nitride (CN) has attracted tremendous attention as heterogeneous (photo)catalysts. </a><a></a><a>By following prototype of enzymes, making all catalytic sites of accessible via homogeneous reactions is a promising approach toward maximizing CN activity, but hindered due to </a><a></a><a>the poor insolubility of CN</a>. Herein, we report the dissolution of CN in environment-friendly methane sulfonic acid and the homogeneous photocatalysis driven by CN for the first time with the activity boosted up to 10-times, comparing to the heterogeneous counterparts. Moreover, facile recycling and reusability, the <a>hallmark</a> of heterogeneous catalysts, were kept for the homogeneous CN photocatalyst via reversible precipitation using poor solvents. It opens new vista of CN in homogeneous catalysis and offers a successful example of polymeric catalysts in bridging gaps of homo/heterogeneous catalysis.

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