Wentuan Bi

Single-Atom Pt as Co-Catalyst for Enhanced Photocatalytic H2 Evolution

Isolated single-atom platinum (Pt) embedded in the sub-nanoporosity of 2D g-C3 N4 as a new form of co-catalyst is reported. The highly stable single-atom co-catalyst maximizes the atom efficiency and alters the surface trap states of g-C3 N4 , leading to significantly enhanced photocatalytic H2 evolution activity, 8.6 times higher than that of Pt nanoparticles and up to 50 times that for bare g-C3 N4 .

Exclusive Ni–N4 Sites Realize Near-Unity CO Selectivity for Electrochemical CO2 Reduction

Electrochemical reduction of carbon dioxide (CO2) to value-added carbon products is a promising approach to reduce CO2 levels and mitigate the energy crisis. However, poor product selectivity is still a major obstacle to the development of CO2 reduction. Here we demonstrate exclusive Ni-N4 sites through a topo-chemical transformation strategy, bringing unprecedentedly high activity and selectivity for CO2 reduction. Topo-chemical transformation by carbon layer coating successfully ensures preservation of the Ni-N4 structure to a maximum extent and avoids the agglomeration of Ni atoms to particles, providing abundant active sites for the catalytic reaction. The Ni-N4 structure exhibits excellent activity for electrochemical reduction of CO2 with particularly high selectivity, achieving high faradaic efficiency over 90% for CO in the potential range from -0.5 to -0.9 V and gives a maximum faradaic efficiency of 99% at -0.81 V with a current density of 28.6 mA cm-2. We anticipate exclusive catalytic sites will shed new light on the design of high-efficiency electrocatalysts for CO2 reduction.

New aspects of size-dependent metal-insulator transition in synthetic single-domain monoclinic vanadium dioxide nanocrystals

Nanoscale materials with size smaller than the characteristic domain size could simplify the domain structure and uncover the intrinsic properties in detail. Herein, a ultrafast open space calcination pathway is first put forward to synthesize high-quality single-domain VO(2)(M) nanocrystals and an in situ variable-temperature IR spectroscopy is first proposed to identify the size-dependent MIT behaviors in VO(2)(M) below single-domain size. The variable-temperature IR spectroscopy clearly reveals that these single-domain VO(2)(M) nanocrystals exhibit new size-dependent MIT behaviors, while the IR analysis further suggests that the size-related defect density and scattering efficiency could be used to account for their novel size-dependent MIT behaviors. This new characterization strategy of in situ variable-temperature IR spectroscopy holds great promise for extending to other systems to gain valuable insight into their intrinsic phase transition behaviors. Also, this ultrafast open space calcination pathway sets forth a new avenue in fabricating high-quality functional nanocrystals and paves the way for constructing intelligent nanodevices in the near future.

In-Plane Coassembly Route to Atomically Thick Inorganic–Organic Hybrid Nanosheets

Control over the anisotropic assembly of small building blocks into organized structures is considered an effective way to design organic nanosheets and atomically thick inorganic nanosheets with nonlayered structure. However, there is still no available route so far to control the assembly of inorganic and organic building blocks into a flattened hybrid nanosheet with atomic thickness. Herein, we highlight for the first time a universal in-plane coassembly process for the design and synthesis of transition-metal chalcogenide-alkylamine inorganic-organic hybrid nanosheets with atomic thickness. The structure, formation mechanism, and stability of the hybrid nanosheets were investigated in detail by taking the Co₉S₈-oleylamine (Co₉S₈-OA) hybrid nanosheets as an example. Both experimental data and theoretical simulations demonstrate that the hybrid nanosheets were formed by in-plane connection of small two-dimensional (2D) Co₉S₈ nanoplates via oleylamine molecules adsorbed at the side surface and corner sites of the nanoplates. X-ray absorption fine structure spectroscopy study reveals the structure distortion of the small 2D Co₉S₈ nanoplates that endows structural stability of the atomically thick Co₉S₈-OA hybrid nanosheets. The brand new atomically thick nanosheets with inorganic-organic hybrid network nanostructure will not only enrich the family of atomically thick 2D nanosheets but also inspire more interest in their potential applications.

Metallic mesocrystal nanosheets of vanadium nitride for high-performance all-solid-state pseudocapacitors

AbstractTransition metal nitrides (TMNs) are of particular interest by virtue of their synergic advantages of superior electrical conductivity, excellent environmental durability and high reaction selectivity, yet it is difficult to achieve flexible design and operation. Herein, mesocrystal nanosheets (MCNSs) of vanadium nitride (VN) are synthesized via a confined-growth route from thermally stable layered vanadium bronze, representing the first two-dimensional (2D) metallic mesocrystal in inorganic compounds. Benefiting from their single-crystalline-like long-range electronic connectivity, VN MCNSs deliver an electrical conductivity of 1.44 × 105 S/m at room temperature, among the highest values observed for 2D nanosheets. Coupled with their unique pseudocapacitance, VN MCNS-based flexible supercapacitors afford a superior volumetric capacitance of 1,937 mF/cm3. Nitride MCNSs should have wide applications in the energy storage and conversion fields because their intrinsic high conductivity is coupled with the reactivity of inorganic lattices.

Surface Immobilization of Transition Metal Ions on Nitrogen‐Doped Graphene Realizing High‐Efficient and Selective CO2 Reduction

Electrochemical conversion of CO2 to value-added chemicals using renewable electricity provides a promising way to mitigate both global warming and the energy crisis. Here, a facile ion-adsorption strategy is reported to construct highly active graphene-based catalysts for CO2 reduction to CO. The isolated transition metal cyclam-like moieties formed upon ion adsorption are found to contribute to the observed improvements. Free from the conventional harsh pyrolysis and acid-leaching procedures, this solution-chemistry strategy is easy to scale up and of general applicability, thus paving a rational avenue for the design of high-efficiency catalysts for CO2 reduction and beyond.

Moisture-triggered actuator and detector with high-performance: interface engineering of graphene oxide/ethyl cellulose

Actuators that can directly convert other forms of environmental energy into mechanical work offer great application prospects in intriguing energy applications and smart devices. But to-date, low cohesion strength of the interface and humidity responsive actuators primarily limit their applications. Herein, by experimentally optimizing interface of bimorph structure, we build graphene oxide/ethyl cellulose bidirectional bending actuators—a case of bimorphs with fast and reversible shape changes in response to environmental humidity gradients. Meanwhile, we employ the actuator as the engine to drive piezoelectric detector. In this case, graphene oxide and ethyl cellulose are combined with chemical bonds, successfully building a bimorph with binary synergy strengthening and toughening. The excellent hygroscopicity of graphene oxide accompanied with huge volume expansion triggers giant moisture responsiveness greater than 90 degrees. Moreover, the open circuit voltage of piezoelectric detector holds a peak value around 0.1 V and exhibits excellent reversibility. We anticipate that humidity-responsive actuator and detector hold promise for the application and expansion of smart devices in varieties of multifunctional nanosystems.摘要致动器可以将外界环境中的能量直接转换成机械能, 在能源应用和智能设备上有着广阔的应用前景. 但迄今为止, 界面接触强度较低以及湿度响应是制约驱动器发展的瓶颈问题, 限制了其实际应用. 本文从实验上构建了优化双层膜结构驱动器界面接触的模型, 所构建的氧化石墨烯与乙基纤维素双层膜致动器对于环境湿度的变化具有快速可逆的响应性, 同时可以驱动压电探测器. 此结构模型中, 氧化石墨烯与乙基纤维素之间通过化学键结合, 成功地构建了机械强度和韧性协同增强的双层膜驱动器. 由于氧化石墨烯的优异吸湿特性, 同时伴随着明显的体积膨胀, 引起双层膜驱动器对于湿度变化超过90度弯曲的响应. 同时, 构建的压电传感器具有优异可逆性的0.1 V开路电压. 我们期望湿度响应驱动器和传感器有望在各种多功能纳米系统中得到应用并能服务于智能设备领域.

Surface etching induced ultrathin sandwich structure realizing enhanced photocatalytic activity

Photocatalytic conversion efficiency is limited by serious charge carrier recombination. Efficient carrier separation is usually achieved by elegantly-designed multi-component structures connected by directional electric field. Herein, we developed a two-dimensional (2D) sandwich structure, as a new photocatalytic system, to realize high-efficiency carrier separation. This strategy integrated multifunction into a single structure for the first time, which successfully introduces a stable built-in electric field, realizing high-effective carrier separation. Besides, the carrier concentration is dramatically increased due to dimensional confinement. Benefiting from above synergic advantages, 2D sandwich photocatalyst achieves the highest nitrogen fixation rate (435 μmol g−1 h−1) in inorganic solid photocatalysts under visible light irradiation. We anticipate that 2D sandwich photocatalyst holds promises for the application and expansion of 2D materials in photocatalysis research.

Surface-adsorbed ions on TiO2 nanosheets for selective photocatalytic CO2 reduction

A method based on the adsorption of ions on the surface of two-dimensional (2D) nanosheets has been developed for photocatalytic CO2 reduction. Isolated Bi ions, confined on the surface of TiO2 nanosheets using a simple ionic adsorption method facilitate the formation of a built-in electric field that effectively promotes charge carrier separation. This leads to an improved performance of the photocatalytic CO2 reduction process with the preferred conversion to CH4. The proposed surface ion-adsorption method is expected to provide an effective approach for the design of highly efficient photocatalytic systems. These findings could be very valuable in photocatalytic CO2 reduction applications.