Linking Composition, Structure and Thickness of CoOOH layers to Oxygen Evolution Reaction Activity by Correlative Microscopy.

The role of β-CoOOH crystallographic orientations in catalytic activity for the oxygen evolution reaction (OER) remains elusive. We combine correlative electron backscatter diffraction/scanning electrochemical cell microscopy with X-ray photoelectron spectroscopy, transmission electron microscopy, and atom probe tomography to establish the structure-activity relationships of various faceted β-CoOOH formed on a Co microelectrode under OER conditions. We reveal that ≈6 nm β-CoOOH(01 0), grown on [ 0]-oriented Co, exhibits higher OER activity than ≈3 nm β-CoOOH(10 3) or ≈6 nm β-CoOOH(0006) formed on [02 - and [0001]-oriented Co, respectively.

Probing the Gold/Water Interface with Surface-Specific Spectroscopy.

Water is an integral component in electrochemistry, in the generation of the electric double layer, and in the propagation of the interfacial electric fields into the solution; however, probing the molecular-level structure of interfacial water near functioning electrode surfaces remains challenging. Due to the surface-specificity, sum-frequency-generation (SFG) spectroscopy offers an opportunity to investigate the structure of water near working electrochemical interfaces but probing the hydrogen-bonded structure of water at this buried electrode-electrolyte interface was thought to be impossible. Propagating the laser beams through the solvent leads to a large attenuation of the infrared light due to the absorption of water, and interrogating the interface by sending the laser beams through the electrode normally obscures the SFG spectra due to the large nonlinear response of conduction band electrons.

Disproportionation of Nitric Oxide at a Surface-Bound Nickel Porphyrinoid.

Uncommon metal oxidation states in porphyrinoid cofactors are responsible for the activity of many enzymes. The F and P450nor co-factors, with their reduced Ni- and Fe-containing tetrapyrrolic cores, are prototypical examples of biological systems involved in methane formation and in the reduction of nitric oxide, respectively. Herein, using a comprehensive range of experimental and theoretical methods, we raise evidence that nickel tetraphenyl porphyrins deposited in vacuo on a copper surface are reactive towards nitric oxide disproportionation at room temperature.

Disproportionation of Nitric Oxide at a Surface-Bound Nickel Porphyrinoid.

Uncommon metal oxidation states in porphyrinoid cofactors are responsible for the activity of many enzymes. The F and P450nor co-factors, with their reduced Ni - and Fe -containing tetrapyrrolic cores, are prototypical examples of biological systems involved in methane formation and in the reduction of nitric oxide, respectively. Herein, using a comprehensive range of experimental and theoretical methods, we raise evidence that nickel tetraphenyl porphyrins deposited in vacuo on a copper surface are reactive towards nitric oxide disproportionation at room temperature.

Single CoO Nanocubes Electrocatalyzing the Oxygen Evolution Reaction: Nano-Impact Insights into Intrinsic Activity and Support Effects.

Single-entity electrochemistry allows for assessing electrocatalytic activities of individual material entities such as nanoparticles (NPs). Thus, it becomes possible to consider intrinsic electrochemical properties of nanocatalysts when researching how activity relates to physical and structural material properties. Conversely, conventional electrochemical techniques provide a normalized sum current referring to a huge ensemble of NPs constituting, along with additives (e.

Self-Metalation of Porphyrins at the Solid-Gas Interface.

Self-metalation is a promising route to include a single metal atom in a tetrapyrrolic macrocycle in organic frameworks supported by metal surfaces. The molecule-surface interaction may provide the charge transfer and the geometric distortion of the molecular plane necessary for metal inclusion. However, at a metal surface the presence of an activation barrier can represent an obstacle that cannot be compensated by a higher substrate temperature without affecting the layer integrity.

Interplay between CO Disproportionation and Oxidation: On the Origin of the CO Reaction Onset on Atomic Layer Deposition-Grown Pt/ZrO Model Catalysts.

Pt/ZrO model catalysts were prepared by atomic layer deposition (ALD) and examined at mbar pressure by sum frequency generation (SFG) spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) combined with differentially pumped mass spectrometry (MS). ALD enables creating model systems ranging from Pt nanoparticles to bulk-like thin films. Polarization-dependent SFG of CO adsorption reveals both the adsorption configuration and the Pt particle morphology.

Substrate- to Laterally-Driven Self-Assembly Steered by Cu Nanoclusters: The Case of FePcs on an Ultrathin Alumina Film.

We show that, for the formation of a metallorganic monolayer, it is possible to artificially divert from substrate- to laterally-driven self-assembly mechanisms by properly tailoring the corrugation of the potential energy surface of the growth template. By exploiting the capability of an ultrathin alumina film to host metallic nanoparticle seeds, we tune the symmetry of a iron phthalocyanine (FePc) two-dimensional crystal, thus showing that it is possible to switch from trans to lateral dominating interactions in the controlled growth of an organic/inorganic heterostack. Finally, by selecting the size of the metallic clusters, we can also control the FePc-metal interaction strength.

Experimental and Theoretical Investigation of the Restructuring Process Induced by CO at Near Ambient Pressure: Pt Nanoclusters on Graphene/Ir(111).

The adsorption of CO on Pt nanoclusters grown in a regular array on a template provided by the graphene/Ir(111) Moiré was investigated by means of infrared-visible sum frequency generation vibronic spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy from ultrahigh vacuum to near-ambient pressure, and ab initio simulations. Both terminally and bridge bonded CO species populate nonequivalent sites of the clusters, spanning from first to second-layer terraces to borders and edges, depending on the particle size and morphology and on the adsorption conditions. By combining experimental information and the results of the simulations, we observe a significant restructuring of the clusters.

Carbon dioxide reduction on Ir(111): stable hydrocarbon surface species at near-ambient pressure.

Stable hydrocarbon surface species in the carbon dioxide hydrogenation reaction on Ir(111) were identified by means of infrared-visible sum-frequency generation vibrational spectroscopy and X-ray photoelectron spectroscopy under near-ambient pressure conditions (0.1 mbar). By introducing gas phase binary and ternary mixtures of CO2, CO, and H2 into the reaction chamber, stable ethylidyne and ethynyl species were found at the metal surface above 425 K, in remarkable analogy with that observed during the ethylene decomposition process yielding graphene.