Nanoassemblies of ultrasmall clusters with remarkable activity in carbon dioxide conversion into C1 fuels

Sub-picosecond photodynamics of small neutral copper oxide clusters

The ultrafast dynamics of neutral copper oxide clusters (CunOx, n < 5) are reported using femtosecond pump probe spectroscopy in the gas phase. The transient spectra recorded for each cluster demonstrate they relax on a 100s of fs timescale followed by a long-lived (>50 ps) response. Density functional theory calculations are performed to determine the lowest energy structures and spin states. Topological descripters for the excited states are calculated (time-dependent density functional theory) to relate the measured excited state dynamics to changes in the cluster's electronic structure with increasing oxidation. Strong field ionization is demonstrated here to be a soft form of ionization and able to record transient signals for clusters previously determined to be unstable to nanosecond multiphoton ionization. The relative cluster stability is further demonstrated by signal enhancement/depreciation that is recorded through the synergy from the two laser pulses. Once the oxygen atoms exceed the number of copper atoms, a weakly bound superoxide O2 unit forms, exhibiting a higher spin state. All clusters that are not in the lowest spin configuration demonstrate fragmentation.

Gas-phase synthesis of nanoparticles: current application challenges and instrumentation development responses

Nanoparticles constitute fundamental building blocks required in several fields of application with current global importance. To fully exploit nanoparticle properties specifically determined by the size, shape, chemical composition and interfacial configuration, rigorous nanoparticle growth and deposition control is needed. Gas-phase synthesis, in particular magnetron-sputtering inert-gas condensation, provides unique opportunities to realise engineered nanoparticles optimised for the desired use case. Here, we provide an overview of recent nanoparticle growth experiments via this technique, how the latter can meet application-specific requirements, and what challenges might impede the wide-spread adoption for scalable industrial synthesis. More specifically, we discuss the timely topics of energy, catalysis, and sensing applications enabled by gas-phase synthesised nanoparticles, as well as recently emerging advances in neuromorphic devices for unconventional computing. Having identified the most relevant challenges and limiting factors, we outline how advances in nanoparticle source instrumentation and/or in situ diagnostics can address current shortcomings. Eventually we identify common trends and directions, giving our perspective on the most promising and impactful applications of gas-phase synthesised nanoparticles in the future.

Mechanism of Catalytic CO2 Hydrogenation to Methane and Methanol Using a Bimetallic Cu3Pd Cluster at a Zirconia Support

For very small nanocluster-based catalysts, the exploration of the influence of the particle size, composition, and support offers precisely variable parameters in a wide material search space to control catalysts' performance. We present the mechanism of the CO₂ methanation reaction on the oxidized bimetallic Cu₃Pd tetramer (Cu₃PdO₂) supported on a zirconia model support represented by Zr₁₂O₂₄ based on the energy profile obtained from density functional theory calculations on the reaction of CO₂ and H₂. In order to determine the role of the Pd atom, the performance of Cu₃PdO₂ with monometallic Cu₄O₂ at the same support has been compared. Parallel to methane formation, the alternative path of methanol formation at this catalyst has also been investigated. The results show that the exchange of a single atom in Cu₄ with a single Pd atom improves catalyst/s performance via lowering the barriers associated with hydrogen dissociation steps that occur on the Pd atom. The above-mentioned results suggest that the doping strategy at the level of single atoms can offer a precise control knob for designing new catalysts with desired performance.

Exploring the materials space in the smallest particle size range: From heterogeneous catalysis to electrocatalysis and photocatalysis

Ultrasmall clusters of subnanometer size can possess unique and even unexpected physical and chemical propensities which make them interesting in various fields of basic science and for potential applications, such...

Intentional construction of high-performance SnO2 catalysts with a 3D porous structure for electrochemical reduction of CO2

Herein, SnO₂-NC (SnO₂-nanocube) and SnO₂-NF (SnO₂-nanoflake) electro-catalysts featuring a large specific surface area and 3D porous structure were successfully constructed via acid etching and sulfurization-desulphurization methods, respectively. As catalysts for the electrochemical reduction of CO₂, the faradaic efficiency (F_HCOO^-+CO = 82.4%, 91.5%, respectively) and partial current density (j_HCOO^-+CO = 10.7 and 11.5 mA cm^-2, respectively) of SnO₂-NCs and SnO₂-NFs were enhanced in comparison with SnO₂-NPs (SnO₂-nanoparticles, F_HCOO^-+CO = 63.4%, j_HCOO^-+CO = 5.7 mA cm^-2) at -1.0 V vs. RHE. The enhanced catalytic activity is attributed to their uniform 3D porous structure, high specific surface area and excellent wettability. Additionally, the morphology of SnO₂-NCs and SnO₂-NFs was largely preserved after electrolyzing for 12 h (after 12 h of electrolysis), indicating the effective buffering effect of the 3D structure in electrolysis. Naturally, the current density and faradaic efficiency of the SnO₂-NC and SnO₂-NF catalysts remained nearly unchanged after long-term stability measurements, revealing great stability.