Jing Tang

Bio: Jing Tang is an academic researcher from Stanford University. The author has contributed to research in topics: Mesoporous material & Thermoelectric materials. The author has an hindex of 66, co-authored 216 publications receiving 15896 citations. Previous affiliations of Jing Tang include Nanjing University of Aeronautics and Astronautics & University of Wollongong.

Thermal Conversion of Core–Shell Metal–Organic Frameworks: A New Method for Selectively Functionalized Nanoporous Hybrid Carbon

Abstract: Core–shell structured ZIF-8@ZIF-67 crystals are well-designed and prepared through a seed-mediated growth method. After thermal treatment of ZIF-8@ZIF-67 crystals, we obtain selectively functionalized nanoporous hybrid carbon materials consisting of nitrogen-doped carbon (NC) as the cores and highly graphitic carbon (GC) as the shells. This is the first example of the integration of NC and GC in one particle at the nanometer level. Electrochemical data strongly demonstrate that this nanoporous hybrid carbon material integrates the advantageous properties of the individual NC and GC, exhibiting a distinguished specific capacitance (270 F·g–1) calculated from the galvanostatic charge–discharge curves at a current density of 2 A·g–1. Our study not only bridges diverse carbon-based materials with infinite metal–organic frameworks but also opens a new avenue for artificially designed nanoarchitectures with target functionalities.

Nanoarchitectonics for Transition-Metal-Sulfide-Based Electrocatalysts for Water Splitting.

Abstract: Heterogenous electrocatalysts based on transition metal sulfides (TMS) are being actively explored in renewable energy research because nanostructured forms support high intrinsic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, it is described how researchers are working to improve the performance of TMS-based materials by manipulating their internal and external nanoarchitectures. A general introduction to the water-splitting reaction is initially provided to explain the most important parameters in accessing the catalytic performance of nanomaterials catalysts. Later, the general synthetic methods used to prepare TMS-based materials are explained in order to delve into the various strategies being used to achieve higher electrocatalytic performance in the HER. Complementary strategies can be used to increase the OER performance of TMS, resulting in bifunctional water-splitting electrocatalysts for both the HER and the OER. Finally, the current challenges and future opportunities of TMS materials in the context of water splitting are summarized. The aim herein is to provide insights gathered in the process of studying TMS, and describe valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies.

Asymmetric Supercapacitors Using 3D Nanoporous Carbon and Cobalt Oxide Electrodes Synthesized from a Single Metal-Organic Framework.

Abstract: Nanoporous carbon and nanoporous cobalt oxide (Co3O4) materials have been selectively prepared from a single metal–organic framework (MOF) (zeolitic imidazolate framework, ZIF-67) by optimizing the annealing conditions. The resulting ZIF-derived carbon possesses highly graphitic walls and a high specific surface area of 350 m2·g–1, while the resulting ZIF-derived nanoporous Co3O4 possesses a high specific surface area of 148 m2·g–1 with much less carbon content (1.7 at%). When nanoporous carbon and nanoporous Co3O4 were tested as electrode materials for supercapacitor application, they showed high capacitance values (272 and 504 F·g–1, respectively, at a scan rate of 5 mV·s–1). To further demonstrate the advantages of our ZIF-derived nanoporous materials, symmetric (SSCs) and asymmetric supercapacitors (ASCs) were also fabricated using nanoporous carbon and nanoporous Co3O4 electrodes. Improved capacitance performance was successfully realized for the ASC (Co3O4//carbon), better than those of the SSCs bas...

Reduced Mesoporous Co3O4 Nanowires as Efficient Water Oxidation Electrocatalysts and Supercapacitor Electrodes

Abstract: While electrochemical water splitting is one of the most promising methods to store light/electrical energy in chemical bonds, a key challenge remains in the realization of an efficient oxygen evolution reaction catalyst with large surface area, good electrical conductivity, high catalytic properties, and low fabrication cost. Here, a facile solution reduction method is demonstrated for mesoporous Co3O4 nanowires treated with NaBH4. The high-surface-area mesopore feature leads to efficient surface reduction in solution at room temperature, which allows for retention of the nanowire morphology and 1D charge transport behavior, while at the same time substantially increasing the oxygen vacancies on the nanowire surface. Compared to pristine Co3O4 nanowires, the reduced Co3O4 nanowires exhibit a much larger current of 13.1 mA cm-2 at 1.65 V vs reversible hydrogen electrode (RHE) and a much lower onset potential of 1.52 V vs RHE. Electrochemical supercapacitors based on the reduced Co3O4 nanowires also show a much improved capacitance of 978 F g-1 and reduced charge transfer resistance. Density-functional theory calculations reveal that the existence of oxygen vacancies leads to the formation of new gap states in which the electrons previously associated with the Co-O bonds tend to be delocalized, resulting in the much higher electrical conductivity and electrocatalytic activity.

Nanoarchitectured Design of Porous Materials and Nanocomposites from Metal-Organic Frameworks.

Abstract: The emergence of metal-organic frameworks (MOFs) as a new class of crystalline porous materials is attracting considerable attention in many fields such as catalysis, energy storage and conversion, sensors, and environmental remediation due to their controllable composition, structure and pore size. MOFs are versatile precursors for the preparation of various forms of nanomaterials as well as new multifunctional nanocomposites/hybrids, which exhibit superior functional properties compared to the individual components assembling the composites. This review provides an overview of recent developments achieved in the fabrication of porous MOF-derived nanostructures including carbons, metal oxides, metal chalcogenides (metal sulfides and selenides), metal carbides, metal phosphides and their composites. Finally, the challenges and future trends and prospects associated with the development of MOF-derived nanomaterials are also examined.

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

Abstract: The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Metal–Organic Frameworks (MOFs)

Abstract: 슈퍼캐패시터(supercapacitor)는 배터리와 함께 많은 양의 전기에너지를 저장 및 공급하 는 중요한 에너지 저장 장치이다. 특히 슈퍼캐 패시터는 고출력이 가능하고 크기와 형태가 조절가능하여 전자기기 부터 자동차 까지 그 사용분야가 매우 넓다 [1-3]. 최근에 웨어러블 (wearable) 디바이스와 플렉서블(flexible) 전 자기기의 발달과 함께 구부릴 수 있고, 당길 수 있는(stretchable) 슈퍼캐패시터의 개발 또한 활발히 진행되고 있다 [4-8]. 슈퍼캐패시터의 작동원리에 따라 전기이중층 캐패시터(electric double-layer capacitor, EDLC)와 의사캐패시터 (pseudocapacitor)로 나뉜다. EDLC는 전하분 리현상을 이용하기 때문에 넓은 표면적을 갖 는 활성탄(activated carbon)과 같은 전극 재료 를 사용하며 의사캐패시터는 전극 재료의 산 화·환원반응(reduction and oxidation, redox) 을 이용하므로 redox반응을 잘 일으키면서 넓 은 표면적을 갖는 전도성 고분자와 금속산화 물 등의 전극 재료를 사용하게된다 [9]. 슈퍼캐 패시터의 전극 재료로서 높은 에너지 저장능 력 및 성능을 갖으려면, 일반적으로 높은 표면 적을 갖도록 해야하며, 슈퍼캐패시터의 성능 은 전극 활물질의 모폴로지(morphology), 기 공크기분포(pore size distribution), 전기전도 도(electrical conductivity), 표면 특성, 열 특성 등의 다양한 성질에 의해 결정되며, 이를 최적 화 했을 때 높은 성능의 슈퍼캐패시터의 제조 가 가능하다 [1]. 일반적으로 다공성 구조의 카 본 및 금속산화물을 만들기 위해서 그 재료의 전구체를 계면활성제(surfactant)를 이용하여 모폴러지 및 다공성을 조절하였다. 계면활성 제의 사용은 다양한 모양과 구조의 활물질제 조를 가능하게 하였지만, 많은 양의 계면활성 제의 사용은 시약의 가격, 후처리, 환경적인 측 면에서 단점을 가진다. 금속유기구조체(metal-organic frameworks, MOFs)는 금속이온과 유기물 연결체(organic linker)로 만들어진 조성물로서, 합성 시 이러한 추가적인 계면활성제의 사용없이 매우 높은 표 면적을 갖는 금속유기 조성물을 만들 수 있다 (그림 1). 이러한 MOF는 사용되는 금속이온, 유 기연결체, 결정구조 등에 따라 MOF-N, HKUSTN, ZIF-N 등 (N: number)으로 구분되어 명명된 다 (그림 1(b)) [10, 11] . 또한, 사용하는 금속이 온과 유기물 연결체의 종류에 따라 다공성 특 성을 조절할 수 있고, 이들의 열처리를 통해서 다공성 카본체 및 금속산화물의 제조가 가능하 다 [12]. 더욱이, MOF는 기존의 다양한 재료에 적용이 가능하여 다양한 에너지저장 재료로 만 들어 질 수 있으며, 나노기술 및 다양한 접근 방 법을 통해 나노구조체 및 조성물의 합성이 가 능하다 [13]. 이러한 장점으로 인해 최근 많은 종류의 MOF 물질들이 슈퍼캐패시터 및 2차전 지의 에너지 저장시스템(energy storage systems, ESSs) 에 응용되고 있다 (그림 2). MOF 중 이미다졸(imidazole) 유도체를 유기연결체로

Ultracapacitors: Why, How, and Where is the Technology

Abstract: The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

The photoluminescence mechanism in carbon dots (graphene quantum dots, carbon nanodots, and polymer dots): current state and future perspective

Abstract: At present, the actual mechanism of the photoluminescence (PL) of fluorescent carbon dots (CDs) is still an open debate among researchers. Because of the variety of CDs, it is highly important to summarize the PL mechanism for these kinds of carbon materials; doing so can guide the development of effective synthesis routes and novel applications. This review will focus on the PL mechanism of CDs. Three types of fluorescent CDs were involved: graphene quantum dots (GQDs), carbon nanodots (CNDs), and polymer dots (PDs). Four reasonable PL mechanisms have been confirmed: the quantum confinement effect or conjugated π-domains, which are determined by the carbon core; the surface state, which is determined by hybridization of the carbon backbone and the connected chemical groups; the molecule state, which is determined solely by the fluorescent molecules connected on the surface or interior of the CDs; and the crosslink-enhanced emission (CEE) effect. To give a thorough summary, the category and synthesis routes, as well as the chemical/physical properties for the CDs, are briefly introduced in advance.