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The design of efficient and stable photocatalysts for robust CO 2 reduction without sacrifice reagent or extra photosensitizer is still challenging. Herein, a single-atom catalyst of isolated single atom cobalt incorporated into Bi 3 O 4 Br atomic layers is successfully prepared. The cobalt single atoms in the Bi 3 O 4 Br favors the charge transition, carrier separation, CO 2 adsorption and activation. It can lower the CO 2 activation energy barrier through stabilizing the COOH* intermediates and tune the rate-limiting step from the formation of adsorbed intermediate COOH* to be CO* desorption. Taking advantage of cobalt single atoms and two-dimensional ultrathin Bi 3 O 4 Br atomic layers, the optimized catalyst can perform light-driven CO 2 reduction with a selective CO formation rate of 107.1 µmol g −1 h −1 , roughly 4 and 32 times higher than that of atomic layer Bi 3 O 4 Br and bulk Bi 3 O 4 Br, respectively.

Metal-halide perovskites represent a class of promising light absorbers for efficient solar cells. [1][2][3][4][5] The propensity of perovskite films for low-cost solution processing also encourages scientists to explore potential applications beyond solar cells. [6][7][8][9] In particular, as emitters, perovskites exhibit intriguing luminescent properties such as narrowband emission, spectral tunability, and high quantum efficiency, which enables applications in the microlasers and light-emitting diodes (LEDs). [10][11][12][13] The luminescence efficiency of perovskites generally relies on nanostructures that can spatially confine excitons, and consequently reduce the possibility of nonradiative recombination during the carrier/ exciton migration. However, nanocrystals, due to boundary scattering of carriers, generally face the problem of poor charge transport, which is undesirable for LED performance. 2D perovskites, where bulky organic layers and inorganic layers are alternately and periodically arranged, feature natural quantum-well structures. This quantum-well structure is regarded as promising LED emitters for decades. [14][15][16] However, low photoluminescence quantum yields (PLQYs, typically < 1%) of 2D perovskites at room temperature is a bottleneck to achieving high-performance LEDs. [17] The low PLQYs may be attributed to insufficient confinement of Wannier type excitons within the inorganic layers [18] as suggested by the long charge-carrier/exciton diffusion length (60 nm). [19] Engineering crystal structures of low-dimensional (0D to 2D) perovskites by employing suitable organic ammonium cations is the predominant methods for the tuning of luminescence, both in spectral coverage and efficiency. [20,21] In these cases, severe structural distortion of metal halide octahedra is a common feature because of the size mismatch between organic and inorganic components, which results in potential fluctuations. [22,23] Such fluctuations of potential within an inorganic layer of perovskite sometimes, but not always, [20,21] slow the diffusion of carriers or excitons, and consequently induce self-trapped excitons (STEs), which represents a type of bound states for efficient radiative recombination. However, the occurrence of exciton self-trapping in semiconductors is the exception rather than the rule. [24] In parallel, compositional engineering As emerging efficient emitters, metal-halide perovskites offer the intriguing potential to the low-cost light emitting devices. However, semiconductors generally suffer from severe luminescence quenching due to insufficient confinement of excitons (bound electron-hole pairs). Here, Sn-triggered extrinsic self-trapping of excitons in bulk 2D perovskite crystal, PEA 2 PbI 4 (PEA = phenylethylammonium), is reported, where exciton self-trapping never occurs in its pure state. By creating local potential wells, isoelectronic Sn dopants initiate the localization of excitons, which would further induce the large lattice deformation around the impurities to accommodate the se...

Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

A graphene-like coordination polymer based on copper(II) benzenehexathiol (Cu-BHT, 1) with high electric conductivity (10 S·cm) was prepared recently. The high conductivity makes this material a good candidate for electrocatalysis, and here its catalytic activity toward hydrogen evolution reaction (HER) was evaluated. Cu-BHT shows good activity and stability for HER in acidic solutions under high current densities. By changing the preparation conditions, the morphology of Cu-BHT materials was controlled at the mesoscale, which allows the preparation of a thin film (TF-1), nanocrystal (NC-1), and amorphous nanoparticle (NP-1) of Cu-BHT. The overpotential of Cu-BHT toward HER shows an improved activity from 760 mV (NC-1) to 450 mV (NP-1) at a current density of 10 mA·cm. A Tafel slope of ∼95 mV·dec and an exchange current density of 10 mA·cm were achieved under optimized conditions. Density functional theory calculations suggest that the "Cu-edge site" on the (100) surface plays an important role in improving the HER catalytic performance of Cu-BHT nanoparticles.