Carbon nanothreads are a new one-dimensional sp carbon nanomaterial. They assemble into hexagonal crystals in a room temperature, nontopochemical solid-state reaction induced by slow compression of benzene to 23 GPa. Here we show that pyridine also reacts under compression to form a well-ordered sp product: CNH carbon nitride nanothreads. Solid pyridine has a different crystal structure from solid benzene, so the nontopochemical formation of low-dimensional crystalline solids by slow compression of small aromatics may be a general phenomenon that enables chemical design of properties. The nitrogen in the carbon nitride nanothreads may improve processability, alters photoluminescence, and is predicted to reduce the bandgap.

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Metal electrodes with rough surfaces are often found to convert CO or CO2 to hydrocarbons and oxygenates with high selectivity and at high reaction rates in comparison with their smooth counterparts. The atomic-level morphology of a rough electrode is likely one key factor responsible for its comparatively high catalytic selectivity and activity. However, few methods are capable of probing the atomic-level structure of rough metal electrodes under electrocatalytic conditions. As a result, the nuances in the atomic-level surface morphology that control the catalytic characteristics of these electrodes have remained largely unexplored. Because the CO stretching frequency of atop-bound CO (COatop) depends on the coordination of the underlying metal atom, the IR spectrum of this reaction intermediate on the copper electrode could, in principle, provide structural information about the catalytic surface during electrolysis. However, other effects, such as dynamic dipole coupling, easily obscure the dependence of the frequency on the surface morphology. Further, in the limit of low COatop coverage, where coupling effects are small, the CO stretching frequencies of COatop on Cu(111) and Cu(100) facets are virtually identical. Therefore, on the basis of the CO stretching frequency, it is not straightforward to distinguish between these two ubiquitous surface facets, which exhibit vastly different CO reduction activities. Herein, we show that key features of the atomic-level surface morphology of rough copper electrodes can be inferred from the potential dependence of the line shape of the CO stretching band of COatop. Specifically, we compared two types of rough copper thin-film electrodes that are routinely employed in the context of surface-enhanced infrared absorption spectroscopy (SEIRAS). We found that copper films that are electrochemically deposited on Si-supported Au films (CuAu–Si) are poor catalysts for the reduction of CO to ethylene in comparison to copper films (Cu–Si) that are electrolessly deposited onto Si crystals. As quantified by differential electrochemical mass spectrometry (DEMS), the onset potential for ethylene is ∼200 ± 65 mV more cathodic for CuAu–Si than that for Cu–Si. To reveal the origin of the disparate catalytic properties of Cu–Si and CuAu–Si, we probed the surfaces of the electrodes with cyclic voltammetry (CV) and SEIRAS. The CV characterization suggests that the (111) surface facet predominates on CuAu–Si, whereas the (100) facet is more common on Cu–Si. SEIRAS reveals that the line shape of the CO stretching of COatop is composed of two bands that are attributable to COatop on terrace and defect sites. The different surface structures manifest themselves in the form of starkly different potential dependences of the line shape of the CO stretching mode of COatop on the two types of electrodes. With a simple Boltzmann model that considers the different adsorption energies of COatop on terrace and defect sites, and the resulting COatop populations on terrace and defect sites, we de...

As a promising high-temperature fuel cell, the direct carbon fuel cell (DCFC) has a much higher efficiency and a lower emission as compared with conventional coal-fired power plants. To develop an increased understanding of the relationship between the microstructure, surface chemistry, and electrochemical performance of coal as a fuel for the DCFC, a coal sample from Central Queensland has been subjected to various pretreatments, including acid washing, air oxidation, and pyrolysis. It has been found that an acid treatment of the coal enhanced its electrochemical reactivity due to an increase in oxygen-containing surface functional groups. By contrast, heat treatment of the coal results in a sharp decrease in the electrochemical reactivity in the DCFC due to a decrease in the oxygen-containing surface functional groups, particularly CO(2)-yielding surface groups. A higher surface area of coal may also be helpful, but much less important than surface chemistry.