Ruchun Li

Large Scale Synthesis of NiCo Layered Double Hydroxides for Superior Asymmetric Electrochemical Capacitor.

We report a new environmentally-friendly synthetic strategy for large-scale preparation of 16 nm-ultrathin NiCo based layered double hydroxides (LDH). The Ni50Co50-LDH electrode exhibited excellent specific capacitance of 1537 F g−1 at 0.5 A g−1 and 1181 F g−1 even at current density as high as 10 A g−1, which 50% cobalt doped enhances the electrical conductivity and porous and ultrathin structure is helpful with electrolyte diffusion to improve the material utilization. An asymmetric ultracapacitor was assembled with the N-doped graphitic ordered mesoporous carbon as negative electrode and the NiCo LDH as positive electrode. The device achieves a high energy density of 33.7 Wh kg−1 (at power density of 551 W kg−1) with a 1.5 V operating voltage.

Metal-free N-doped carbon nanofibers as an efficient catalyst for oxygen reduction reactions in alkaline and acid media

The development of metal-free catalysts to replace the use of Pt has played an important role in relation to its application to fuel cells. We report N-doped carbon nanofibers as the catalyst of an oxygen reduction reaction, which were synthesized via carbonizing bacterial cellulose-polypyrrole composites. The as-prepared material exhibited remarkable catalytic activity toward the oxygen reduction reaction with comparable onset potential and the ability to limit the current density of commercial Pt/C catalysts in both alkaline and acid media due to the unique porous three-dimensional network structure and the doped nitrogen atoms. The effect of N functionalities on catalytic behavior was systematically investigated. The results demonstrated that pyridinic-N was the dominating factor for catalytic performance toward the oxygen reduction reaction. Additionally, N-doped carbon nanofibers also demonstrated excellent cycling stability (93.2% and 89.4% retention of current density after chronoamperometry 20 000 s in alkaline and media, respectively), obviously superior to Pt/C.

Fe/N co-doped carbon microspheres as a high performance electrocatalyst for the oxygen reduction reaction

Recently, nitrogen-doped carbon materials have attracted immense interest because of their great potential in various applications. In this work, FeN-doped carbon microspheres are large-scale synthesized using basic magnesium carbonate as the template and glycine as the carbon and nitrogen precursor by a simple liquid impregnation method under a relatively low pyrolysis temperature. Iron is introduced into the carbon microspheres to enhance the graphitic degree and improve the electrocatalytic performance. This carbon material with high specific area, high nitrogen content and part-graphitization shows high activity and four-electron selectivity for the oxygen reduction reaction in an alkaline medium. Compared to a commercial Pt/C catalyst, this material presents exceeding stability and durability, which can be a candidate for potential applications in the fuel cell and electrochemical industries of oxygen reduction.