Enhancing Efficiency and High-Value Chemicals Generation through Coupling Photocatalytic CO Reduction with Propane Oxidation.

Conversion of CO into high-value chemicals using solar energy is one of promising approaches to achieve carbon neutrality. However, the oxidation of water in the photocatalytic CO reduction is kinetically unfavorable due to multi-electron and proton transfer processes, along with the difficulty in generating O-O bonds. To tackle these challenges, this study investigated the coupling reaction of photocatalytic CO reduction and selective propane oxidation using the Pd/P25 (1 wt%) catalyst.

Generating active metal/oxide reverse interfaces through coordinated migration of single atoms.

Identification of active sites in catalytic materials is important and helps establish approaches to the precise design of catalysts for achieving high reactivity. Generally, active sites of conventional heterogeneous catalysts can be single atom, nanoparticle or a metal/oxide interface. Herein, we report that metal/oxide reverse interfaces can also be active sites which are created from the coordinated migration of metal and oxide atoms.

Confined Cu-OH single sites in SSZ-13 zeolite for the direct oxidation of methane to methanol.

The direct oxidation of methane to methanol (MTM) remains a significant challenge in heterogeneous catalysis due to the high dissociation energy of the C-H bond in methane and the high desorption energy of methanol. In this work, we demonstrate a breakthrough in selective MTM by achieving a high methanol space-time yield of 2678 mmol molCu-1 h-1 with 93% selectivity in a continuous methane-steam reaction at 400 °C. The superior performance is attributed to the confinement effect of 6-membered ring (6MR) voids in SSZ-13 zeolite, which host isolated Cu-OH single sites.

Mechanistic Insights into Radical-Induced Selective Oxidation of Methane over Nonmetallic Boron Nitride Catalysts.

Boron-based nonmetallic materials (such as BO and BN) emerge as promising catalysts for selective oxidation of light alkanes by O to form value-added products, resulting from their unique advantage in suppressing CO formation. However, the site requirements and reaction mechanism of these boron-based catalysts are still in vigorous debate, especially for methane (the most stable and abundant alkane). Here, we show that hexagonal BN (-BN) exhibits high selectivities to formaldehyde and CO in catalyzing aerobic oxidation of methane, similar to AlO-supported BO catalysts, while -BN requires an extra induction period to reach a steady state.

Distinct Role of Surface Hydroxyls in Single-Atom Pt/CeO Catalyst for Room-Temperature Formaldehyde Oxidation: Acid-Base Versus Redox.

The development of highly efficient catalysts for room-temperature formaldehyde (HCHO) oxidation is of great interest for indoor air purification. In this work, it was found that the single-atom Pt/CeO catalyst exhibits a remarkable activity with complete removal of HCHO even at 288 K. Combining density functional theory calculations and DRIFTS experiments, it was revealed that the active OH site generated on CeO in the vicinity of Pt via steam treatment plays a key role in the oxidation of HCHO to formate and its further oxidation to CO.

Synergetic Effect of Mo, Mg-Modified Sn-β Over Moderate-Temperature Conversion of Hexose to Alkyl Lactate.

The thermocatalytic conversion of hexose into valuable chemicals such as methyl lactate under mild conditions is very appealing. Here, we report that Mo, Mg co-modified Sn-β catalyst can effectively catalyze the transformation of glucose and fructose into alkyl lactate at moderate temperatures. A maximum yield of around 35% of methyl lactate was achieved from the conversion of glucose in methanol at 100°C over Sn-β catalyst modified with 3 wt% Mo and 0.

Confinement-Enhanced Selective Oxidation of Lignin Derivatives to Formic Acid Over Fe-Cu/ZSM-5 Catalysts Under Mild Conditions.

Aqueous-phase oxidation by H O , known as the Fenton-type process, provides an attractive route to convert recalcitrant lignin derivatives to valuable chemicals under mild conditions. The development of this technology is, however, limited by the uncontrolled selectivity, resulting from the highly reactive nature of H O and the thermodynamically favored deep oxidation to form CO . This study demonstrated that formic acid could be produced with a high selectivity (up to 80.

Hydrogen spillover assisted by oxygenate molecules over nonreducible oxides.

Spontaneous migration of atomic hydrogen species from metal particles to the surface of their support, known as hydrogen spillover, has been claimed to play a major role in catalytic processes involving hydrogen. While this phenomenon is well established on reducible oxide supports, its realization on much more commonly used non-reducible oxides is still challenged. Here we present a general strategy to enable effective hydrogen spillover over non-reducible SiO with aid of gaseous organic molecules containing a carbonyl group.

Noble Metal Single-Atom Catalysts for the Catalytic Oxidation of Volatile Organic Compounds.

Invited for this month's cover is the group of Haifeng Xiong at Xiamen University. The image shows that single-atom catalysts can work in the catalytic oxidation of volatile organic compounds. The Review itself is available at 10.

Shape-Dependent Performance of Cu/Cu O for Photocatalytic Reduction of CO.

The photocatalytic conversion of CO into solar fuels or chemicals is a sustainable approach to relieve the immediate problems related to global warming and the energy crisis. This study concerns the effects of morphological control on a Cu/Cu O-based photocatalyst for CO reduction. The as-synthesized spherical Cu/Cu O photocatalyst exhibits higher activity than the octahedral one under visible light irradiation.

Noble Metal Single-Atom Catalysts for the Catalytic Oxidation of Volatile Organic Compounds.

Volatile organic compounds (VOCs) are detrimental to the environment and human health and must be eliminated before discharging. Oxidation by heterogeneous catalysts is one of the most promising approaches for the VOCs abatement. Precious metal catalysts are highly active for the catalytic oxidation of VOCs, but they are rare and their high price limits large-scale application.

Direct conversion of methane to formaldehyde and CO on BO catalysts.

Direct oxidation of methane to value-added C chemicals (e.g. HCHO and CO) provides a promising way to utilize natural gas sources under relatively mild conditions.

Propane oxidative dehydrogenation over highly selective hexagonal boron nitride catalysts: The role of oxidative coupling of methyl.

Hexagonal boron nitride (-BN) catalyst has recently been reported to be highly selective in oxidative dehydrogenation of propane (ODHP) for olefin production. In addition to propene, ethylene also forms with much higher overall selectivities to C2-products than to C1-products. In this work, we report that the reaction pathways over the -BN catalyst are different from the V-based catalysts in ODHP.

Direct Coupling of Thermo- and Photocatalysis for Conversion of CO -H O into Fuels.

Photocatalytic CO reduction into renewable hydrocarbon solar fuels is considered as a promising strategy to simultaneously address global energy and environmental issues. This study focused on the direct coupling of photocatalytic water splitting and thermocatalytic hydrogenation of CO in the conversion of CO -H O into fuels. Specifically, it was found that direct coupling of thermo- and photocatalysis over Au-Ru/TiO leads to activity 15 times higher (T=358 K; ca.

A Strategy for the Simultaneous Synthesis of Methallyl Alcohol and Diethyl Acetal with Sn-β.

A new strategy was developed to simultaneously produce two important chemicals, namely, methallyl alcohol (Mol) and diethyl acetal (Dal) from methacrolein in ethanol solvent at low temperature with the use of Beta zeolites modified by tin (Sn-β catalysts). All the Sn-β catalysts were prepared by the solid-state ion-exchange method, wherein the calcination step was conducted under different gas atmospheres. The catalyst precalcined in Ar (Sn-β-Ar) had a reduced number of extra-framework Sn species and enabled more Sn species to be exchanged into the framework as isolated tetrahedral Sn , enhancing the catalytic activity of the Meerwein-Ponndorf-Verley (MPV) reaction.

A General Time-Periodic Driving Approach to Realize Topological Phases in Cold Atomic Systems.

For time-reversal symmetric cold atomic insulating systems, it is found that the usual driving approach based on electromagnetic field used in solid state systems loses its power to drive them from trivial regimes to topological regimes if the driven systems still hold time-reversal symmetry (TRS). For such systems, we point out that simply varying the optical lattice potential periodically provides a general and effective way to drive them into topological regimes without breaking their symmetries. Based on this approach, we find that the time-reversal symmetric Kane-Mele model can be effectively driven from the trivial phase to topological phases named as Floquet Quantum Spin Hall insulator.

Topological Superfluid and Majorana Zero Modes in Synthetic Dimension.

Recently it has been shown that multicomponent spin-orbit-coupled fermions in one-dimensional optical lattices can be viewed as spinless fermions moving in two-dimensional synthetic lattices with synthetic magnetic flux. The quantum Hall edge states in these systems have been observed in recent experiments. In this paper we study the effect of an attractive Hubbard interaction.

Decoupling HZSM-5 catalyst activity from deactivation during upgrading of pyrolysis oil vapors.

The independent evaluation of catalyst activity and stability during the catalytic pyrolysis of biomass is challenging because of the nature of the reaction system and rapid catalyst deactivation that force the use of excess catalyst. In this contribution we use a modified pyroprobe system in which pulses of pyrolysis vapors are converted over a series of HZSM-5 catalysts in a separate fixed-bed reactor controlled independently. Both the reactor-bed temperature and the Si/Al ratio of the zeolite are varied to evaluate catalyst activity and deactivation rates independently both on a constant surface area and constant acid site basis.

Surface spectral function of momentum-dependent pairing potentials in a topological insulator: application to CuxBi2Se3.

We propose three possible momentum-dependent pairing potentials as candidates for topological superconductors (for example CuxBi2Se3), and calculate the surface spectral function and surface density of states with these pairing potentials. We find that the first two can give the same spectral functions as the fully gapped and node-contacted pairing potentials given by Fu and Berg (2010 Phys. Rev.

The quantum anomalous Hall effect on a star lattice with spin-orbit coupling and an exchange field.

We study a star lattice with Rashba spin-orbit coupling and an exchange field and find that there is a quantum anomalous Hall effect in this system, and that there are five energy gaps at Dirac points and quadratic band crossing points. We calculate the Berry curvature distribution and obtain the Hall conductivity (Chern number ν) quantized as integers, and find that ν =- 1,2,1,1,2 when the Fermi level lies in these five gaps. Our model can be viewed as a general quantum anomalous Hall system and, in limit cases, can give what the honeycomb lattice and kagome lattice give.

Fractional charge and statistics in the fractional quantum spin Hall effect.

In this paper, we consider there exist two types of fundamental quasihole excitation in the fractional quantum spin Hall state and investigate their topological properties by both Chern-Simons field theory and the Berry phase technique. By the two different techniques, we obtain the identical charge and statistical angle for each type of quasihole, as well as the identical mutual statistics between two different types of quasihole excitation.

Orbital diamagnetism of weakly doped bilayer graphene in a magnetic field.

We investigate the orbital diamagnetism of weakly doped bilayer graphene (BLG) in a spatially smoothly varying magnetic field and obtain the general analytic expression for the orbital susceptibility of BLG, with finite wavenumber and Fermi energy, at zero temperature. We find that the magnetic field screening factor of BLG is dependent on the wavenumber, which results in a more complicated screening behavior compared with that of monolayer graphene (MLG). We also study the induced magnetization and electric current in BLG, under a nonuniform magnetic field, and find that they are qualitatively different from those for MLG and the two-dimensional electron gas (2DEG).

Improvements on a gravity-driven low-rate particle feeder.

A gravity-driven particle feeder has been modified to achieve sustained operation at steady rates. Particle reservoirs and rod for controlling the nozzle opening are completely redesigned. Particle attrition and rod wobbling are the two main contributors to the feed instabilities.

A gravity-driven low-rate particle feeder.

A gravity-driven particle feeder has been designed, fabricated, and tested to feed particles at low rates. A solenoid and a digital timer regulate the feed rate. This design avoids moving parts at the system periphery and thus avoids possible air leakages.

Directional ordering of fluctuations in a two-dimensional compass model.

In the Mott insulating phase of the transition metal oxides, the effective orbital-orbital interaction is directional both in orbital space and in real space. We discuss a classical realization of directional coupling in two dimensions. Despite extensive degeneracy of the ground state, the model exhibits partial orbital ordering in the form of directional ordering of fluctuations at low temperatures stabilized by an entropy gap.