Cheng Tang

Bio: Cheng Tang is an academic researcher from Queensland University of Technology. The author has contributed to research in topics: Graphene & Electrocatalyst. The author has an hindex of 48, co-authored 147 publications receiving 9403 citations. Previous affiliations of Cheng Tang include Shandong University & Queen Mary University of London.

A Review of Electrocatalytic Reduction of Dinitrogen to Ammonia under Ambient Conditions

Abstract: DOI: 10.1002/aenm.201800369 reactions involved.[1] In recent years, tremendous progress has been achieved in the field of heterogeneous electrocatalysis, with rapid development of multifarious electocatalysts toward oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction reaction (CO2RR). However, electrocatalysts for the reduction of dinitrogen (N2) to ammonia (NH3) at room temperature and atmospheric pressure remain largely underexplored, despite the fact that investigations on catalysts and reaction systems for artificial nitrogen fixation have been continued for more than 100 years.[2–4] Ammonia is primarily used for producing fertilizers to sustain the world’s population.[5] It also serves as a green energy carrier and a potential transportation fuel.[6] Currently, ammonia synthesis is dominated by the industrial Haber–Bosch process using heterogeneous iron-based catalysts at high temperature (300–500 °C) and high pressure (150–300 atm),[7] accounting for more than 1% of the world’s energy supply and generating more than 300 million metric tons of fossil fuel–derived CO2 annually.[8,9] Hence, it is desirable to develop alternative processes that have the potential to overcome the limitations of the Haber–Bosch process including harsh conditions, complex plant infrastructure, centralized distribution, high energy consumption, and negative environmental impacts. In nature, biological N2 fixation occurs under mild conditions via nitrogenase enzymes that contain FeMo, FeV, or FeFe cofactor as catalytic active sites.[10,11] Developed man-made catalysts are therefore stimulated to reduce N2 upon the addition of protons and electrons, which is similar to the nitrogenase catalytic process. Transition metal–dinitrogen complexes such as the molybdenum–, iron–, and cobalt–dinitrogen complexes have been proposed as homogeneous catalysts for the reduction of N2 into NH3 under ambient conditions;[12] however, the stability and recycling issues are challenging.[13] On the other hand, electrochemical and photochemical reduction processes using heterogeneous catalysts benefit from clean and renewable energy sources and are promising for achieving NH3 production directly from N2 and water.[14] The electrochemical reduction of N2 to NH3 can be more efficient than the photochemical counterpart. This is because not all of the photons in the photochemical reduction process can The production of ammonia (NH3) from molecular dinitrogen (N2) under mild conditions is one of the most attractive topics in the field of chemistry. Electrochemical reduction of N2 is promising for achieving clean and sustainable NH3 production with lower energy consumption using renewable energy sources. To date, emerging electrocatalysts for the electrochemical reduction of N2 to NH3 at room temperature and atmospheric pressure remain largely underexplored. The major challenge is to achieve both high catalytic activity and high selectivity. Here, the recent progress on the electrochemical nitrogen reduction reaction (NRR) at ambient temperature and pressure from both theoretical and experimental aspects is summarized, aiming at extracting instructive perceptions for future NRR research activities. The prevailing theories and mechanisms for NRR as well as computational screening of promising materials are presented. State-of-the-art heterogeneous electrocatalysts as well as rational design of the whole electrochemical systems for NRR are involved. Importantly, promising strategies to enhance the activity, selectivity, efficiency, and stability of electrocatalysts toward NRR are proposed. Moreover, ammonia determination methods are compared and problems relating to possible ammonia contamination of the system are mentioned so as to shed fresh light on possible standard protocols for NRR measurements.

Nanocarbon for Oxygen Reduction Electrocatalysis: Dopants, Edges, and Defects.

Abstract: The oxygen reduction reaction (ORR) is the cornerstone of various sustainable energy-conversion technologies. Metal-free nanocarbon electrocatalysts with competitive activity, enhanced durability, and satisfactory cost, have been proposed as the most promising substitute for precious-metal catalysts. However, their further development is still primarily based on trial-and-error approaches due to the controversial knowledge of critical active sites and mechanisms. Herein, the activity origins of nanocarbon-based ORR electro-catalysts are comprehensively reviewed and correlated, considering the dopants, edges, and defects. Analogously, they can effectively modify the charge/spin distribution on the sp2 -conjugated carbon matrix, leading to optimized intermediate chemisorption and facilitated electron transfer. Specific doping at defective edges is expected to render practical applications for metal-free nanocarbon electrocatalysts.

Spatially Confined Hybridization of Nanometer-Sized NiFe Hydroxides into Nitrogen-Doped Graphene Frameworks Leading to Superior Oxygen Evolution Reactivity.

Abstract: Nanometer-sized hydroxide active centers are uniformly and strongly hybridized into a graphene framework by means of defect-anchored nucleation and spatially confined growth, resulting in a superior electrocatalyst for oxygen evolution reaction. This family of strongly coupled complexes and the topology-assisted fabrication strategy is expected to open up new avenues of research. It sheds light on a novel branch of advanced nano-architectured materials.

Defect Engineering toward Atomic Co–Nx–C in Hierarchical Graphene for Rechargeable Flexible Solid Zn-Air Batteries

Abstract: Rechargeable flexible solid Zn-air battery, with a high theoretical energy density of 1086 Wh kg−1, is among the most attractive energy technologies for future flexible and wearable electronics; nevertheless, the practical application is greatly hindered by the sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics on the air electrode. Precious metal-free functionalized carbon materials are widely demonstrated as the most promising candidates, while it still lacks effective synthetic methodology to controllably synthesize carbocatalysts with targeted active sites. This work demonstrates the direct utilization of the intrinsic structural defects in nanocarbon to generate atomically dispersed Co–Nx–C active sites via defect engineering. As-fabricated Co/N/O tri-doped graphene catalysts with highly active sites and hierarchical porous scaffolds exhibit superior ORR/OER bifunctional activities and impressive applications in rechargeable Zn-air batteries. Specifically, when integrated into a rechargeable and flexible solid Zn-air battery, a high open-circuit voltage of 1.44 V, a stable discharge voltage of 1.19 V, and a high energy efficiency of 63% at 1.0 mA cm−2 are achieved even under bending. The defect engineering strategy provides a new concept and effective methodology for the full utilization of nanocarbon materials with various structural features and further development of advanced energy materials.

Topological Defects in Metal-Free Nanocarbon for Oxygen Electrocatalysis.

Abstract: A bifunctional graphene catalyst with abundant topological defects is achieved via the carbonization of natural gelatinized sticky rice to probe the underlying oxygen electrocatalytic mechanism A nitrogen-free configuration with adjacent pentagon and heptagon carbon rings is revealed to exhibit the lowest overpotential for both oxygen reduction and evolution catalysis The versatile synthetic strategy and novel insights on the activity origin facilitate the development of advanced metal-free carbocatalysts for a wide range of electrocatalytic applications

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...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Abstract: Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...