The CO oxidation behaviors on single Au atom embedded in two-dimensional h-BN monolayer are investigated on the basis of first-principles calculations, quantum Born-Oppenheim molecular dynamic ...simulations (BOMD) and micro-kinetic analysis. We show that CO oxidation on h-BN monolayer support single gold atom prefers an unreported tri-molecular Eley-Rideal (E-R) reaction, where O2 molecule is activated by two pre-adsorbed CO molecules. The formed OCOAuOCO intermediate dissociates into two CO2 molecules synchronously, which is the rate-limiting step with an energy barrier of 0.47 eV. By using the micro-kinetic analysis, the CO oxidation following the tri-molecular E-R reaction pathway entails much higher reaction rate (1.43 × 10(5) s(-1)) than that of bimolecular Langmuir-Hinshelwood (L-H) pathway (4.29 s(-1)). Further, the quantum BOMD simulation at the temperature of 300 K demonstrates the complete reaction process in real time.
In many organic reactions, the O2 activation process involves a key step where inert ground triplet O2 is excited to produce highly reactive singlet O2. It remains elusive what factor induces the ...change in the electron spin state of O2 molecules, although it has been discovered that the presence of noble metal nanoparticles can promote the generation of singlet O2. In this work, we first demonstrate that surface facet is a key parameter to modulate the O2 activation process on metal nanocrystals, by employing single-facet Pd nanocrystals as a model system. The experimental measurements clearly show that singlet O2 is preferentially formed on {100} facets. The simulations further elucidate that the chemisorption of O2 to the {100} facets can induce a spin–flip process in the O2 molecules, which is achieved via electron transfer from Pd surface to O2. With the capability of tuning O2 activation, we have been able to further implement the {100}-faceted nanocubes in glucose oxidation. It is anticipated that this study will open a door to designing noble metal nanocatalysts for O2 activation and organic oxidation. Another perspective of this work would be the controllability in tailoring the cancer treatment materials for high 1O2 production efficiency, based on the facet control of metal nanocrystals. In the cases of both organic oxidation and cancer treatment, it has been exclusively proven that the efficiency of producing singlet O2 holds the key to the performance of Pd nanocrystals in the applications.
A Ru3+‐mediated synthesis for the unique Pd concave nanostructures, which can directly harvest UV‐to‐visible light for styrene hydrogenation, is described. The catalytic efficiency under 100 mW cm−2 ...full‐spectrum irradiation at room temperature turns out to be comparable to that of thermally (70 °C) driven reactions. The yields obtained with other Pd nanocrystals, such as nanocubes and octahedrons, are lower. The nanostructures reported here have sufficient plasmonic cross‐sections for light harvesting in a broad spectral range owing to the reduced shape symmetry, which increases the solution temperature for the reaction by the photothermal effect. They possess a large quantity of atoms at corners and edges where local heat is more efficiently generated, thus providing active sites for the reaction. Taken together, these factors drastically enhance the hydrogenation reaction by light illumination.
Taking shape: A Ru3+‐mediated synthesis has been developed for unique Pd concave nanostructures which can directly harvest UV‐to‐visible light for styrene hydrogenation (see figure). The catalytic efficiency under full‐spectrum irradiation at room temperature turns out to be comparable to that of the thermally (70 °C) driven reaction. The yields are higher than those obtained using Pd nanocrystals such as nanocubes and octahedrons.
Pt(100) facets are generally considered less active for the oxygen reduction reaction (ORR). Reported herein is a unique Pt‐branched structure, a multicube, whose surface is mostly enclosed by {100} ...facets but contains high‐index facets at the small junction area between the adjacent cubic components. The synthesis is accomplished by a Ni2+‐mediated facet evolution from high‐index {311} to {100} facets on the frameworks of multipods. Despite the high {100} facet coverage, the Pt multicubes exhibit impressive ORR activity in terms of half‐wave potential and current density nearly to the level of the most active Pt‐based catalysts, while the durability of catalysts is well retained. The facet evolution creates a set of samples with tunable ratios of high‐index to low‐index facets. The results reveal that the excellent ORR performance of Pt multicubes is a combined result of active sites by high‐index facets and low resistance by flat surface. It is anticipated that this work will offer a new approach to facet‐controlled synthesis and ORR catalysts design.
Facet to facet: A Ni2+‐mediated facet‐evolution approach has been developed to synthesize novel Pt multicubes whose surface is mostly enclosed by {100} facets. The Pt multicubes exhibit very high electrocatalytic activity and remarkable durability in the oxygen reduction reaction because of the high‐index facets at the junction between the cubic components.
Methyl halides are versatile platform molecules, which have been widely adopted as precursors for producing value-added chemicals and fuels. Despite their high importance, the green and economical ...synthesis of the methyl halides remains challenging. Here we demonstrate sustainable and efficient photocatalytic methane halogenation for methyl halide production over copper-doped titania using alkali halides as a widely available and noncorrosive halogenation agent. This approach affords a methyl halide production rate of up to 0.61 mmol h
m
for chloromethane or 1.08 mmol h
m
for bromomethane with a stability of 28 h, which are further proven transformable to methanol and pharmaceutical intermediates. Furthermore, we demonstrate that such a reaction can also operate solely using seawater and methane as resources, showing its high practicability as general technology for offshore methane exploitation. This work opens an avenue for the sustainable utilization of methane from various resources and toward designated applications.
Developing carbon-based electrocatalysts with excellent N
2
adsorption and activation capability holds the key to achieve highly efficient nitrogen reduction reaction (NRR) for reaching its practical ...application. Here, we report a highly active electrocatalyst—metal-free pyrrolic-N dominated N, S co-doped carbon (pyrr-NSC) for NRR. Based on theoretical and experimental results, it is confirmed that the N and S-dopants practice a working-in-tandem mechanism on pyrr-NSC, where the N-dopants are utilized to create electropositive C sites for enhancing N
2
adsorption and the S-dopants are employed to induce electron backdonation for facilitating N
2
activation. The synergistic effect of the pyrrolic-N and S-dopants can also suppress the irritating hydrogen evolution reaction, further boosting the NRR performance. This work gives an indication that the combination of two different dopants on electrocatalyst can enhance NRR performance by working in the two tandem steps—the adsorption and activation of N
2
molecules, providing a new strategy for NRR electrocatalyst design.
Perfect boron nitride (BN) nanotubes are chemically inert, and hardly considered as catalysts. Nevertheless, metal wire encapsulated BN nanotubes show extraordinarily high chemical activity. We ...report nickel (Ni) nanowire encapsulated BN(8.0) and BN(9.0) nanotubes toward O
2
activation and CO oxidization on the basis of first-principles calculations. Our results suggest that Ni wire encapsulated BN(8.0) and BN(9.0) nanotubes can easily adsorb and activate O
2
molecules to form peroxo or superoxo species exothermically. Meanwhile, superoxo species are ready to react with CO molecules forming OCOO intermediate state and finally yielding CO
2
molecules. Meanwhile, the rate-limiting step barrier is only 0.637 eV, implying excellent performance for CO oxidation on Ni nanowire encapsulated BN nanotubes. Furthermore, encapsulation of nickel wire improves the catalytic activity of BN nanotubes by facilitating electron transfer from Ni wire to BN nanotubes, which facilitates the adsorption of highly electronegative O
2
molecules and subsequent CO oxidation. This study provides a practical and efficient strategy for activating O
2
on a metal encapsulated BN nanotube toward CO oxidation.
Anodic oxygen evolution reaction (OER) is the key bottleneck for water electrolysis technique owing to its sluggish reaction kinetics. Interfacial engineering on the rationally designed ...heterostructure can regulate the electronic states efficiently for intrinsic activity improvement. Here, we report a co-phosphorization approach to construct a VPO4-Ni2P heterostructure on nickel foam with strongly chemical binding, wherein phosphate acts as electronic modifier for Ni2P electrocatalyst. Profiting from the interfacial interaction, it is uncovered that electron shifts from Ni2P to VPO4 to render valence increment in Ni species. Such an electronic manipulation rationalizes the chemical affinities of various oxygen intermediates in OER pathway, giving a substantially reduced energy barrier. As a result, the advanced VPO4-Ni2P heterostructure only requires an overpotential of 289 mV to deliver a high current density of 350 mA/cm2 for OER in alkaline electrolyte, together with a Tafel slope as low as 28 mV/dec. This work brings fresh insights into interfacial engineering for advanced electrocatalyst design.
In this work, we construct a VPO4-Ni2P heterostructure electrocatalyst on nickel foam to achieve the electron transfer from Ni2P to VPO4 through interfacial engineering. This electronic manipulation rationalizes the chemical affinities of various oxygen intermediates, thus enhancing the electrochemical oxygen evolution activity. Display omitted
Non-platinum-group (NPG) single-metal-atom electrocatalysts with bifunctional catalytic capabilities for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly sought for ...producing sustainable and renewable energy sources. Doping nonmetal atoms next to the active single-metal-atom can be an effective way to further improve the overall catalytic activities. Herein, we report a nonmetal B-doping strategy for enhancing the catalytic activity of the graphene-based single-metal-atom Mn-pyridine-N4-graphene catalysts named MnN4B n -G (n = 0–8) toward ORR and OER. The underlying chemical mechanism for this design is that the B dopant can lower the charge density corresponding to the d-orbital of the Mn atom, thereby weakening the adsorption strength of oxygen intermediates (O/OH/OOH) on the active Mn site, leading to higher ORR electrocatalytic activity. Not only can this doping strategy enhance ORR activity, but it can also retain high OER activity. Our results show that the MnN4B5-G catalyst entails both relatively high onset potential for ORR (U onset = 0.78 V) and relatively low overpotential for OER (ηover = 0.43 V), rendering it being a compelling oxygen redox bifunctional electrocatalyst. The newly designed single-metal-atom Mn-pyridine-N4-graphene catalysts offer alternative NPG metals and bifunctional catalysts for renewable energy applications.
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