Zhonghua Ren

Bio: Zhonghua Ren is an academic researcher from Harbin Institute of Technology. The author has contributed to research in topics: Graphene & Supercapacitor. The author has an hindex of 12, co-authored 19 publications receiving 527 citations.

Graphene/MoS2/FeCoNi(OH)x and Graphene/MoS2/FeCoNiPx multilayer-stacked vertical nanosheets on carbon fibers for highly efficient overall water splitting

Abstract: Development of excellent and cheap electrocatalysts for water electrolysis is of great significance for application of hydrogen energy. Here, we show a highly efficient and stable oxygen evolution reaction (OER) catalyst with multilayer-stacked hybrid structure, in which vertical graphene nanosheets (VGSs), MoS2 nanosheets, and layered FeCoNi hydroxides (FeCoNi(OH)x) are successively grown on carbon fibers (CF/VGSs/MoS2/FeCoNi(OH)x). The catalyst exhibits excellent OER performance with a low overpotential of 225 and 241 mV to attain 500 and 1000 mA cm−2 and small Tafel slope of 29.2 mV dec−1. Theoretical calculation indicates that compositing of FeCoNi(OH)x with MoS2 could generate favorable electronic structure and decrease the OER overpotential, promoting the electrocatalytic activity. An alkaline water electrolyzer is established using CF/VGSs/MoS2/FeCoNi(OH)x anode for overall water splitting, which generates a current density of 100 mA cm−2 at 1.59 V with excellent stability over 100 h. Our highly efficient catalysts have great prospect for water electrolysis. While water-splitting electrocatalysis offers a renewable means for carbon-neutral energy production, it is a challenge to design efficient, active, and stable catalysts. Here, authors prepare multilayer composite nanosheet materials as bifunctional water-splitting electrocatalysts.

3D Graphene Fibers Grown by Thermal Chemical Vapor Deposition

Abstract: 3D assembly of graphene sheets (GSs) is important for preserving the merits of the single-atomic-layered structure. Simultaneously, vertical growth of GSs has long been a challenge for thermal chemical vapor deposition (CVD). Here, vertical growth of the GSs is achieved in a thermal CVD reactor and a novel 3D graphene structure, 3D graphene fibers (3DGFs), is developed. The 3DGFs are prepared by carbonizing electrospun polyacrylonitrile fibers in NH3 and subsequently in situ growing the radially oriented GSs using thermal CVD. The GSs on the 3DGFs are densely arranged and interconnected with the edges fully exposed on the surface, resulting in high performances in multiple aspects such as electrical conductivity (3.4 × 104 -1.2 × 105 S m-1 ), electromagnetic shielding (60 932 dB cm2 g-1 ), and superhydrophobicity and superoleophilicity, which are far superior to the existing 3D graphene materials. With the extraordinary properties along with the easy scalability of the simple thermal CVD, the novel 3DGFs are highly promising for many applications such as high-strength and conducting composites, flexible conductors, electromagnetic shielding, energy storage, catalysis, and separation and purification. Furthermore, this strategy can be widely used to grow the vertical GSs on many other substrates by thermal CVD.

Aligned polyaniline nanowires grown on the internal surface of macroporous carbon for supercapacitors

Abstract: High utilization efficiency of electrode materials is of great importance for achieving excellent electrochemical performance of supercapacitors. In this paper, we report the growth of aligned polyaniline (PANI) nanowires on the internal surface of macroporous carbon (MC) derived from luffa sponge fibers for increasing their utilization efficiency. The pores in the MC are densely packed, straight, and parallel with the diameter at the micrometer scale, which provide easy paths for reaction solution to penetrate and thus enable the growth of the PANI nanowires on the internal wall surface. Due to full exposure to the electrolyte, the PANI nanowires exhibit high utilization efficiency, leading to high specific capacitance up to 1500 F g−1 (1 A g−1). As the macropores allow easy penetration of the electrolyte, the PANI nanowires show high rate capability with the capacitance retention up to 70% with increasing current density from 1 to 10 A g−1. Symmetric supercapacitors assembled using the MC/PANI materials possess high energy density (19 W h kg−1 at 0.5 kW kg−1) and long cycle life (83% retention after 7000 cycles). Considering the abundance and green production of the luffa sponge the MC/PANI composites are promising for industrial application of supercapacitors.

Large-scale synthesis of hybrid metal oxides through metal redox mechanism for high-performance pseudocapacitors.

Abstract: Electrochemical performance and production cost are the main concerns for the practical application of supercapacitors. Here we report a simple and universally applicable method to prepare hybrid metal oxides by metal redox reaction utilizing the inherent reducibility of metals and oxidbility of for the first time. As an example, Ni(OH)2/MnO2 hybrid nanosheets (NMNSs) are grown for supercapacitor application by self-reaction of Ni foam substrates in KMnO4 solution at room temperature. The obtained hybrid nanosheets exhibit high specific capacitance (2,937 F g(-1)). The assembled solid-state asymmetric pseudocapacitors possess ultrahigh energy density of 91.13 Wh kg(-1) (at the power density of 750 W kg(-1)) and extraordinary cycling stability with 92.28% capacitance retention after 25,000 cycles. Co(OH)2/MnO2 and Fe2O3/MnO2 hybrid oxides are also synthesized through this metal redox mechanism. This green and low-cost method is capable of large-scale production and one-step preparation of the electrodes, holding promise for practical application of high-performance pseudocapacitors.

Handbook of Chemistry and Physics

Abstract: There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Applications of hierarchically structured porous materials from energy storage and conversion, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine

Abstract: Over the last decade, significant effort has been devoted to the applications of hierarchically structured porous materials owing to their outstanding properties such as high surface area, excellent accessibility to active sites, and enhanced mass transport and diffusion. The hierarchy of porosity, structural, morphological and component levels in these materials is key for their high performance in all kinds of applications. The introduction of hierarchical porosity into materials has led to a significant improvement in the performance of materials. Herein, recent progress in the applications of hierarchically structured porous materials from energy conversion and storage, catalysis, photocatalysis, adsorption, separation, and sensing to biomedicine is reviewed. Their potential future applications are also highlighted. We particularly dwell on the relationship between hierarchically porous structures and properties, with examples of each type of hierarchically structured porous material according to its chemical composition and physical characteristics. The present review aims to open up a new avenue to guide the readers to quickly obtain in-depth knowledge of applications of hierarchically porous materials and to have a good idea about selecting and designing suitable hierarchically porous materials for a specific application. In addition to focusing on the applications of hierarchically porous materials, this comprehensive review could stimulate researchers to synthesize new advanced hierarchically porous solids.

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

Abstract: A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed Additionally, the recent application of Cu-based catalysts for the ORR is reviewed Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided

Materials Design and System Construction for Conventional and New-Concept Supercapacitors

Abstract: With the development of renewable energy and electrified transportation, electrochemical energy storage will be more urgent in the future. Supercapacitors have received extensive attention due to their high power density, fast charge and discharge rates, and long-term cycling stability. During past five years, supercapacitors have been boomed benefited from the development of nanostructured materials synthesis and the promoted innovation of devices construction. In this review, we have summarized the current state-of-the-art development on the fabrication of high-performance supercapacitors. From the electrode material perspective, a variety of materials have been explored for advanced electrode materials with smart material-design strategies such as carbonaceous materials, metal compounds and conducting polymers. Proper nanostructures are engineered to provide sufficient electroactive sites and enhance the kinetics of ion and electron transport. Besides, new-concept supercapacitors have been developed for practical application. Microsupercapacitors and fiber supercapacitors have been explored for portable and compact electronic devices. Subsequently, we have introduced Li-/Na-ion supercapacitors composed of battery-type electrodes and capacitor-type electrode. Integrated energy devices are also explored by incorporating supercapacitors with energy conversion systems for sustainable energy storage. In brief, this review provides a comprehensive summary of recent progress on electrode materials design and burgeoning devices constructions for high-performance supercapacitors.