Mixed-Potential-Driven Catalysis: An Electrochemical Mechanism for Room-Temperature CO Oxidation on Gold Catalysts.

Gold is an effective catalyst for low-temperature CO oxidation, yet its mechanism remains debated. Among the various proposed mechanisms, increasing attention has been given to a possible electrochemical pathway in recent studies. Here, experimental evidence is reported that CO oxidation at room temperature in electrolytes proceeds via coupled electrochemical CO oxidation and oxygen reduction half-reactions, i.

Why Does the Performance of Nitrogen-Doped Carbon Electrocatalysts Decrease in Acidic Conditions?

Nitrogen-doped carbon has emerged as a promising low-cost and durable alternative to platinum catalysts for the oxygen reduction reaction (ORR) in fuel cells. However, its catalytic activity decreases significantly in acidic electrolytes, limiting the practical applications. Here, we report the degradation mechanisms of nitrogen-doped carbon catalysts, focusing on the acid-base equilibrium of pyridinic nitrogen (pyri-N), which serves the primary active site.

Pentagon-Rich Caged Carbon Catalyst for the Oxygen Reduction Reaction in Acidic Electrolytes.

The interaction between electron spin and oxygen molecules in non-platinum catalysts, particularly carbon catalysts, significantly influences the catalytic performance of the oxygen reduction reaction (ORR). A promising approach to developing high-performance catalysts involves introducing five-membered ring structures with spin into graphitic carbons. In this study, we present the successful synthesis of cage-like cubic carbon catalysts enriched with pentagon structures using pentagon ring-containing C and a NaCl template.

Theoretical framework for mixed-potential-driven catalysis.

Mixed-potential-driven catalysis is expected to be a distinctive heterogeneous catalytic reaction that produces products different from those produced by thermal catalytic reactions without the application of external energy. Electrochemically, the mechanism is similar to that of corrosion. However, a theory that incorporates catalytic activity as a parameter has not been established.

Rhombohedral Boron Monosulfide as a p-Type Semiconductor.

Two-dimensional materials have wide ranging applications in electronic devices and catalysts owing to their unique properties. Boron-based compounds, which exhibit a polymorphic nature, are an attractive choice for developing boron-based two-dimensional materials. Among them, rhombohedral boron monosulfide (r-BS) has recently attracted considerable attention owing to its unique layered structure similar to that of transition metal dichalcogenides and a layer-dependent bandgap.

Critical impacts of interfacial water on C-H activation in photocatalytic methane conversion.

On-site and on-demand photocatalytic methane conversion under ambient conditions is one of the urgent global challenges for the sustainable use of ubiquitous methane resources. However, the lack of microscopic knowledge on its reaction mechanism prevents the development of engineering strategies for methane photocatalysis. Combining real-time mass spectrometry and operando infrared absorption spectroscopy with ab initio molecular dynamics simulations, here we report key molecular-level insights into photocatalytic green utilization of methane.

Chemisorption of CO on Nitrogen-Doped Graphitic Carbons.

The adsorption of CO on nitrogen-doped graphitic carbon materials, such as graphene nanosheet (GNS) powder and highly oriented pyrolytic graphite (HOPG), was comparatively studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Desorption of CO was observed at approximately 380 K for both pyridinic-nitrogen (pyri-N)-doped GNS and pyri-N-doped HOPG samples in the TPD experiments, whereas no CO desorption was observed for graphitic nitrogen-doped HOPG. This indicated that only pyri-N species create identical CO adsorption sites on any graphitic carbon surface.

Activating Nitrogen-doped Graphene Oxygen Reduction Electrocatalysts in Acidic Electrolytes using Hydrophobic Cavities and Proton-conductive Particles.

Although pyridinic-nitrogen (pyri-N) doped graphene is highly active for the oxygen reduction reaction (ORR) of fuel cells in alkaline media, the activity critically decreases under acidic conditions. We report on how to prevent the deactivation based on the mechanistic understanding that governs the ORR kinetics. First, we considered that the deactivation is due to the hydration of pyri-NH , leading to a lower shift of the redox potential.

Hollow Spherical Fullerene Obtained by Kinetically Controlled Liquid-Liquid Interfacial Precipitation.

Nanomaterials with hollow structures are expected to exhibit new functionalities for materials engineering. Here we report the fabrication of fullerene (C ) spheres having different hollow structures by using a kinetically controlled liquid-liquid interfacial precipitation (KC-LLIP) method. For this purpose, 1,2-ethylenediamine (EDA) was used as a covalent cross-linker of C molecules to form C -EDA shells, while in-situ generated EDA-sulfur (EDA-S) droplets were applied as 'yolks' being eliminated by washing following formation of the yolk-shell structure, leading to hollow structures.

Hydrogenation of Formate Species Using Atomic Hydrogen on a Cu(111) Model Catalyst.

The reaction mechanism of the CHOH synthesis by the hydrogenation of CO on Cu catalysts is unclear because of the challenge in experimentally detecting reaction intermediates formed by the hydrogenation of adsorbed formate (HCOO). Thus, the objective of this study is to clarify the reaction mechanism of the CHOH synthesis by establishing the kinetic natures of intermediates formed by the hydrogenation of adsorbed HCOO on Cu(111). We exposed HCOO on Cu(111) to atomic hydrogen at low temperatures of 200-250 K and observed the species using infrared reflection absorption (IRA) spectroscopy and temperature-programmed desorption (TPD) studies.

Versatile nanoarchitectonics of Pt with morphology control of oxygen reduction reaction catalysts.

Electro-catalytic activity of Pt in the oxygen reduction reaction (ORR) depends strongly on its morphology. For an understanding of how morphology affects the catalytic properties of Pt, the investigation of Pt materials having well-defined morphologies is required. However, the challenges remain in rational and facile synthesis of Pt particles with tuneable well-defined morphology.

Role of Pyridinic Nitrogen in the Mechanism of the Oxygen Reduction Reaction on Carbon Electrocatalysts.

The introduction of pyridinic nitrogen (pyri-N) into carbon-based electrocatalysts for the oxygen reduction reaction is considered to create new active sites. Herein, the role of pyri-N in such catalysts was investigated from a mechanistic viewpoint using carbon black (CB)-supported pyri-N-containing molecules as model catalysts; the highest activity was observed for 1,10-phenanthroline/CB. X-ray photoemission spectroscopy showed that in acidic electrolytes, both pyri-N atoms of 1,10-phenanthroline could be protonated to form pyridinium ions (pyri-NH ).

Dynamical Quantum Filtering via Enhanced Scattering of para-H on the Orientationally Anisotropic Potential of SrTiO(001).

Quantum dynamics calculation, performed on top of density functional theory (DFT)-based total energy calculations, show dynamical quantum filtering via enhanced scattering of para-H on SrTiO(001). We attribute this to the strongly orientation-dependent (electrostatic) interaction potential between the H (induced) quadrupole moment and the surface electric field gradient of ionic SrTiO(001). These results suggest that ionic surfaces could function as a scattering/filtering media to realize rotationally state-resolved H.

Active Sites and Mechanism of Oxygen Reduction Reaction Electrocatalysis on Nitrogen-Doped Carbon Materials.

The oxygen reduction reaction (ORR) is a core reaction for electrochemical energy technologies such as fuel cells and metal-air batteries. ORR catalysts have been limited to platinum, which meets the requirements of high activity and durability. Over the last few decades, a variety of materials have been tested as non-Pt catalysts, from metal-organic complex molecules to metal-free catalysts.

Two charged states of hydrogen on the SrTiO3(001) surface.

The effects of hydrogen exposure on the electronic structure of two types of SrTiO3(001) surfaces, oxygen-deficient (OD) and nearly-vacancy-free (NVF) surfaces, were investigated with ultraviolet photoemission spectroscopy and nuclear reaction analysis. Upon molecular hydrogen exposure to the OD surface which reveals in-gap states at 1.3 eV below the Fermi level, the in-gap state intensity was reduced to half the initial value at a hydrogen coverage of 0.

Control of the surface electronic structure of SrTiO3(001) by modulation of the density of oxygen vacancies.

The influence of electron irradiation and the subsequent oxygen adsorption on the electronic structure of an SrTiO3(001) surface was investigated by ultraviolet photoemission spectroscopy (UPS). Electron irradiation induced an in-gap state (IGS) as observed by UPS keeping the surface 1 × 1, which is considered to originate from oxygen vacancies on the topmost surface due to the electron-stimulated desorption (ESD) of oxygen. Electron irradiation also caused a downward shift of the valence band maximum, indicating downward band bending and the formation of a conductive layer on the surface.