sunlight for sustainable energy conversion and storage. [1] For renewable and efficient hydrogen production, electrochemical water splitting employing renewable electrical energy is a promising route due to its inherent advantages, including readily available reactant, stable output, and feasibility of large-scale production. [2] However, the large overpotential (η) of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) greatly limited their practical applications. Moreover, due to the thermodynamic limitation, the HER reaction usually prefers to be conducted under strong acidic solution while the OER is conducted under basic solution. [3] Extra energy needs to be supplied in order to maintain the pH differences between those two reactions. It is thus imperative to develop highly active electrocatalysts that can utilize under a wide pH range. At present, the state-ofthe-art electrocatalysts for HER are precious metal Pt-based materials and for OER are costly Ir-or Ru-based oxides. [4] But the high cost, scarcity and unsatisfactory durability of above mentioned catalysts further limit the practical utilization of the water splitting technology. [5] Water splitting requires development of cost-effective multifunctional materials that can catalyze both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) efficiently. Currently, the OER relies on the noble-metal catalysts; since with other catalysts, its operation environment is greatly limited in alkaline conditions. Herein, an advanced water oxidation catalyst based on metallic Co 9 S 8 decorated with single-atomic Mo (0.99 wt%) is synthesized (Mo-Co 9 S 8 @C). It exhibits pronounced water oxidization activity in acid, alkali, and neutral media by showing positive onset potentials of 200, 90, and 290 mV, respectively, which manifests the best Co 9 S 8 -based singleatom Mo catalyst till now. Moreover, it also demonstrates excellent HER performance over a wide pH range. Consequently, the catalyst even outperforms noble metal Pt/IrO 2 -based catalysts for overall water splitting (only requiring 1.68 V in acid, and 1.56 V in alkaline). Impressively, it works under a current density of 10 mA cm −2 with no obvious decay during a 24 h (0.5 m H 2 SO 4 ) and 72 h (1.0 m KOH) durability experiment. Density functional theory (DFT) simulations reveal that the synergistic effects of atomically dispersed Mo with Co-containing substrates can efficiently alter the binding energies of adsorbed intermediate species and decrease the overpotentials of the water splitting.
Growth of covalent organic frameworks (COFs) as single crystals is extremely challenging. Inaccessibility of open‐structured single‐crystal COFs prevents the exploration of structure‐oriented applications. Herein we report for the first time a non‐interpenetrated single‐crystal COF, LZU‐306, which possesses the open structure constructed exclusively via covalent assembly. With a high void volume of 80 %, LZU‐306 was applied to investigate the intrinsic dynamics of reticulated tetraphenylethylene (TPE) as the individual aggregation‐induced‐emission moiety. Solid‐state 2H NMR investigation has determined that the rotation of benzene rings in TPE, being the freest among the reported cases, is as fast as 1.0×104 Hz at 203 K to 1.5×107 Hz at 293 K. This research not only explores a new paradigm for single‐crystal growth of open frameworks, but also provides a unique matrix‐isolation platform to reticulate functional moieties into a well‐defined and isolated state.
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