Platinum (Pt) is the state-of-the-art catalyst for oxygen reduction reaction (ORR), but its high cost and scarcity limit its large-scale use. However, if the usage of Pt reduces to a sufficiently low level, this critical barrier may be overcome. Atomically dispersed metal catalysts with high activity and high atom efficiency have the possibility to achieve this goal. Herein, we report a locally distributed atomic Pt-Co nitrogen-carbon-based catalyst (denoted as A-CoPt-NC) with high activity and robust durability for ORR (267 times higher than commercial Pt/C in mass activity). The A-CoPt-NC shows a high selectivity for the 4e pathway in ORR, differing from the reported 2e pathway characteristic of atomic Pt catalysts. Density functional theory calculations suggest that this high activity originates from the synergistic effect of atomic Pt-Co located on a defected C/N graphene surface. The mechanism is thought to arise from asymmetry in the electron distribution around the Pt/Co metal centers, as well as the metal atoms' coordination with local environments on the carbon surface. This coordination results from N8V4 vacancies (where N8 represents the number of nitrogen atoms and V4 indicates the number of vacant carbon atoms) within the carbon shell, which enhances the oxygen reduction reaction via the so-called synergistic effect.

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Defect engineering is an effective way to modulate the electric states and provide active sites for electrocatalytic reactions. However, most studied oxygen vacancies are unstable and susceptible under the oxygen circumstance. Here, we fabricated cobalt-defected Co 3−x O 4 in situ for an efficient oxygen evolution reaction (OER). XAFS and PALS characterizations show that the crystals have abundant Co vacancies and a distorted structure. DFT calculations indicate that the metal defects lead to obvious electronic delocalization, which enhances the carrier transport to participate in water-splitting reactions along the defective conducting channels and the water adsorption/activation on the catalyst surface. Therefore, cobalt-defected Co 3−x O 4 shows remarkably high OER activity by delivering a much lower overpotential of 268 mV@ 10 mA cm −2 (with a small Tafel slope of 38.2 mV/dec) for OER in KOH electrolyte, in comparison with normal Co 3 O 4 (376 mV), IrO 2 (340 mV), and RuO 2 (276 mV). This work opens up a promising approach to construct electronic delocalization structures in metal oxides for high-performance electrochemical catalysts.

A highly crystalline copper(II) benzenehexathiolate coordination polymer (Cu-BHT) has been prepared. The two-dimensional kagome structure has been confirmed by powder X-ray diffraction, high-resolution transmission electron microscopy, and high-resolution scanning transmission electron microscopy. The as-prepared sample exhibits bulk superconductivity at about 0.25 K, which is confirmed by the zero resistivity, AC magnetic susceptibility, and specific heat measurements. Another diamagnetic transition at about 3 K suggests that there is a second superconducting phase that may be associated with a single layer or few layers of Cu-BHT. It is the first time that superconductivity has been observed in a coordination polymer.

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This review introduces the development and application of a multiscale approach to assess the charge mobility for organic semiconductors, which combines quantum chemistry, Kinetic Monte Carlo (KMC), and molecular dynamics (MD) simulations. This approach is especially applicable in describing a large class of organic semiconductors with intermolecular electronic coupling (V) much less than intramolecular charge reorganization energy (λ), a situation where the band description fails obviously. The charge transport is modeled as successive charge hopping from one molecule to another. We highlight the quantum nuclear tunneling effect in the charge transfer, beyond the semiclassical Marcus theory. Such an effect is essential for interpreting the "paradoxical" experimental finding that optical measurement indicated "local charge" while electrical measurement indicated "bandlike". Coupled MD and KMC simulations demonstrated that the dynamic disorder caused by intermolecular vibration has negligible effect on the carrier mobility. We further apply the approach for molecular design of n-type materials and for rationalization of experimental results. The charge reorganization energy is analyzed through decomposition into internal coordinates relaxation, so that chemical structure contributions to the intramolecular electron-phonon interaction are revealed and give helpful indication to reduce the charge reorganization energy.

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