Jianan Zhang

A dual templating route to three-dimensionally ordered mesoporous carbon nanonetworks: tuning the mesopore type for electrochemical performance optimization

To well understand the effect of the mesopore type of ordered mesoporous carbons (OMCs) on enhancing energy storage and conversion is still a great challenge because of the extreme difficulties in exploring new methods to create OMCs with different types of mesopores. Herein, we develop an intriguing dual-templating co-assembly/hydrothermal approach to realize nanostructure engineering in OMCs with various types of mesopores from three-dimensional (3D) cubic (OMCNW-c) to 2D hexagonal mesopores (OMCNW-h) and 0D mesoporous carbon nanospheres (OMC-S) for their electrochemical performance optimization in supercapacitors and oxygen reduction reactions (ORRs). The results show that OMCNW-c exhibits a specific capacitance of 215 F g−1 at 0.5 A g−1, higher than those of OMCNW-h and OMC-S, good capability and excellent cycling performance with no capacity fading even after 10u2006000 cycles. Furthermore, OMCNW-c shows much better electrocatalytic activity for ORR than OMCNW-h and OMC-S. The present investigations give strong evidence that tuning mesopore type of OMCs can contribute another important factor in enhancing catalysis and energy storage. We believe that the present synthetic strategy for different types of mesoporous nanomaterials with desirable structure and morphology can open a new approach to future novel mesoporous materials for greatly improved catalytic and energy applications.

NiCo-embedded in hierarchically structured N-doped carbon nanoplates for the efficient electrochemical determination of ascorbic acid, dopamine, and uric acid

The development of a highly stable and efficient catalyst for sluggish electrooxidation in the electro-determination for ascorbic acid (AA), dopamine (DA) and uric acid (UA) is extremely important for the long-term operation and commercialization of a biosensor device, but it remains a challenge. Herein, we demonstrated an interesting structure of NiCo alloy nanocrystals embedded in hierarchically structured N-doped carbon nanoplates (NiCo-NPs-in-N/C), which is facilely synthesized via a one-step in situ reduction pyrolysis strategy. The two-dimensional N-doped porous carbon shells not only offered the effective confinement effect of NiCo nanocrystals avoiding detachment, dissolution, migration, and aggregation during catalysis process, but also allowed a fast transport pathway for the access of electrolyte to the NiCo surface. As a result, such an intriguing structure shows superior catalytic activity towards the electrooxidation of AA, DA, and UA. The well-separated voltammetric peaks between AA–DA, DA–UA, and AA–UA at the NiCo-NPs-in-N/C are up to 178, 122, and 300 mV, respectively, which is much better than graphene@N-doped carbon core@shell nanoplate (graphene@N/C) and NiCo alloy. Furthermore, the NiCo-NPs-in-N/C also exhibits good reproducibility and stability. The attractive features of NiCo-NPs-in-N/C make it a promising electrocatalyst for the simultaneous determination of AA, DA, and UA.

Facile fabrication of N-doped hierarchical porous carbon@CNT coaxial nanocables with high performance for energy storage and conversion

Developing a facile and cost-effective design and fabrication method to realize an optimal carbon nanoarchitecture containing hierarchical pores, appropriate N doping and high conductivity for high-performance in energy storage and conversion is still a challenge. Herein, we have facilely achieved an intriguing heterostructure of N-doped hierarchical porous carbon@CNT coaxial nanocables (HPNCNTs) via a one-step carbonization of resorcinol–melamine–formaldehyde resin (RMF)@CNT shell@core nanostructures. Significantly, we have demonstrated that the RMF@CNT shell@core nanostructures, with their inherent microporous structure and proper N-containing functionalities, represent the ideal precursor for realizing carbon heterostructures for electrochemical performance optimization for supercapacitors and in the oxygen reduction reaction (ORR). The results show that the HPNCNTs exhibit a specific capacitance of 284 F g−1, much higher than that of CNTs and most of the reported N-doped carbons, a good rate capability and a robust cycling performance with no capacity fading even after 6000 cycles. Furthermore, HPNCNTs show high electrocatalytic activity for the ORR with an onset potential of −0.04 V (vs. Ag/AgCl), a dominant four-electron pathway (n = 3.84), long-term stability, and excellent resistance to crossover effects superior to that of the commercial Pt/C. The present investigation opens the avenue for creating carbon heterostructures with a desirable porous tissue and morphology through a facile and general route for future high-performance renewable energy storage and conversion devices.

CoS2 nanodots trapped within graphitic structured N-doped carbon spheres with efficient performances for lithium storage

Cobalt sulfide (CoS2)-based nanomaterials are promising electrode materials for various energy storage and conversion applications due to their large specific capacities and catalytic activities. However, CoS2-based nanomaterials are still suffering from their volume expansion, agglomeration and poor cycling stability. Here, we demonstrated an intriguing and effective strategy to confine CoS2 nanodots (<10 nm) within the graphitic carbon walls of porous N-doped carbon spheres (CoS2-in-wall-NCSs), which both avoids the volume change and facilitates the promotion of reaction kinetics in lithium ion batteries (LIBs). Moreover, N-doped carbon spheres (NCSs) with nest-like architectures and graphitic carbon nanoribbons offer an ideal diffusion pathway for electrolyte ions and a highly rapid electron transfer pathway. As a result, the CoS2-in-wall-NCSs still exhibit an excellent performance in LIBs with a high specific capacity of 1080.6 mA h g−1 at a current density of 200 mA g−1 even after 500 cycles, which is much better than those of CoS2 nanoparticles (NPs) in the pores of N-doped carbon spheres (CoS2-in-pore-NCSs), metallic Co NPs embedded in N-doped carbon spheres (Co/NCSs), and NCSs. Even at a current density as high as 1000 mA g−1, a reversible capacity of 735.5 mA h g−1 is obtained for CoS2-in-wall-NCSs.

Dual tuning of 1 D heteroatoms doped porous carbon nanoarchitectures for supercapacitors: the role of balanced P/N doping and core@shell nano-networks

Heteroatoms dual-doped carbon with three dimensional interconnected architecture is a promising candidate as electrode for high performance energy storage, but the rational design and cost-effective preparation of such materials is still a challenge. Herein, intriguing P and N co-doped porous CNT@carbon core@shell nano-networks (PN-CNTs) have been facilely achieved by a one-step carbonization process of N containing CNT@polymer with triphenylphosphine (TPP). Significantly, such interesting structure provides the synergistic effects of the 3D interconnected networks consisting of 1D core–shell structure (offering continuous pathway for electron transport), hierarchical porous texture (acting as ion-buffering reservoirs) and P and N dual-doped (optimizing the electron donor/acceptor characteristics of carbon). With the advantages of heteroatoms dual-doping effect and rational interconnected porous structure, the PN-CNTs exhibit an ultra-high specific capacitance of 332.56 F g−1, much higher than N-doped carbon@carbon nanotubes (284 F g−1) and CNTs (32 F g−1), good rate capability and a robust cycling performance (almost no capacity fading even after 8000 cycles). The present work provides a novel passway to engineering multi-heteroatoms doped carbon with hierarchical nanoarchitectures through a facile and general route for high-performance renewable energy storage.

Sulfuration of an Fe-N-C Catalyst Containing Fe x C/Fe Species to Enhance the Catalysis of Oxygen Reduction in Acidic Media and for Use in Flexible Zn-Air Batteries

During the preparation of atomically dispersed Fe-N-C catalysts, it is difficult to avoid the formation of iron-carbide-containing iron clusters (Fex C/Fe), along with the desired carbon matrix containing dispersed FeNx sites. As a result, an uncertain amount of the oxygen reduction reaction (ORR) occurs, making it difficult to maximize the catalytic efficiency. Herein, sulfuration is used to boost the activity of Fex C/Fe, forming an improved system, FeNC-S-Fex C/Fe, for catalysis involving oxygen. Various spectroscopic techniques are used to define the composition of the active sites, which include Fe-S bonds at the interface of the now-S-doped carbon matrix and the Fex C/Fe clusters. In addition to outstanding activity in basic media, FeNC-S-Fex C/Fe exhibits improved ORR activity and durability in acidic media; its half-wave potential of 0.821 V outperforms the commercial Pt/C catalyst (20%), and its activity does not decay even after 10 000 cycles. Interestingly, the catalytic activity for the oxygen evolution reaction (OER) simultaneously improves. Thus, FeNC-S-Fex C/Fe can be used as a high-performance bifunctional catalyst in Zn-air batteries. Theoretical calculations and control experiments show that the original FeNx active centers are enhanced by the Fex C/Fe clusters and the Fe-S and C-S-C bonds.