Jian-Feng Chen

Bio: Jian-Feng Chen is an academic researcher from Beijing University of Chemical Technology. The author has contributed to research in topics: Packed bed & Particle size. The author has an hindex of 57, co-authored 570 publications receiving 14209 citations.

N,P-Codoped Carbon Networks as Efficient Metal-free Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reactions.

Abstract: The high cost and scarcity of noble metal catalysts, such as Pt, have hindered the hydrogen production from electrochemical water splitting, the oxygen reduction in fuel cells and batteries. Herein, we developed a simple template-free approach to three-dimensional porous carbon networks codoped with nitrogen and phosphorus by pyrolysis of a supermolecular aggregate of self-assembled melamine, phytic acid, and graphene oxide (MPSA/GO). The pyrolyzed MPSA/GO acted as the first metal-free bifunctional catalyst with high activities for both oxygen reduction and hydrogen evolution. Zn-air batteries with the pyrolyzed MPSA/GO air electrode showed a high peak power density (310 W g(-1) ) and an excellent durability. Thus, the pyrolyzed MPSA/GO is a promising bifunctional catalyst for renewable energy technologies, particularly regenerative fuel cells.

Highly efficient electrocatalysts for oxygen reduction based on 2D covalent organic polymers complexed with non-precious metals.

Abstract: A class of 2D covalent organic polymers (COPs) incorporating a metal (such as Fe, Co, Mn) with precisely controlled locations of nitrogen heteroatoms and holes were synthesized from various N-containing metal–organic complexes (for example, metal–porphyrin complexes) by a nickel-catalyzed Yamamoto reaction. Subsequent carbonization of the metal-incorporated COPs led to the formation of COP-derived graphene analogues, which acted as efficient electrocatalysts for oxygen reduction in both alkaline and acid media with a good stability and free from any methanol-crossover/CO-poisoning effects.

Catalysis of Carbon Dioxide Photoreduction on Nanosheets: Fundamentals and Challenges.

Abstract: The transformation of CO2 into fuels and chemicals by photocatalysis is a promising strategy to provide a long-term solution to mitigating global warming and energy-supply problems. Achievements in photocatalysis during the last decade have sparked increased interest in using sunlight to reduce CO2 . Traditional semiconductors used in photocatalysis (e.g. TiO2 ) are not suitable for use in natural sunlight and their performance is not sufficient even under UV irradiation. Some two-dimensional (2D) materials have recently been designed for the catalytic reduction of CO2 . These materials still require significant modification, which is a challenge when designing a photocatalytic process. An overarching aim of this Review is to summarize the literature on the photocatalytic conversion of CO2 by various 2D materials in the liquid phase, with special attention given to the development of novel 2D photocatalyst materials to provide a basis for improved materials.

Colloidal Synthesis of Semiconductor Quantum Dots toward Large Scale Production: A Review

Abstract: The development of green synthetic approaches is one of the key materials challenges in moving toward semiconductor quantum dots (QDs) for large-scale production and commercial applications. This article presents a comprehensive overview on the synthesis of colloidal QDs prepared via chemical approaches in solution phase, with emphasis on green routes which possess the advantages of environment-friendly raw materials, simple operation process, and robust mass-scale production. The approaches for the synthesis of QDs in batch reactors are summarized, including hot-injection organometallic synthesis, noninjection organometallic synthesis, aqueous synthesis and biosynthesis approaches, with some of the concerns on their limitations for scale-up, followed by some continuous synthetic methods aiming for reproducible and large-scale production. Current advances in continuous synthesis of QDs by microfluidic devices, high-gravity reactors, and spray-based techniques are briefly introduced. We also provide some i...

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

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...

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.

Metal-free bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions

Abstract: A co-doped carbon material, methods of making such materials, and electrochemical cells and devices comprising such materials are provided. The co-doped carbon material comprises a mesoporous carbon material doped with nitrogen and phoshporous (NPMC). The present NPMC exhibit catalytic activity for both oxygen reduction reaction and oxygen evolution reaction and may be useful as an electrode in an electrochemical cell and particularly as part of a battery. The present NPMC materials may be used as electrodes in primary zinc-air batteries and in rechargeable zinc-air batteries and many other energy systems.