Yu Wang,Guoxin Zhang,Mang Ma,Yiyan Wang,Ying Zhang,Xiaoming Sun,Zifeng Yan
Solid-phase templates are commonly used for building hollow-structured carbon materials (CMs) but often demand post treatments to remove templates. Herein, we develop an efficient and general method to construct hollow carbonaceous structure via the templating of sacrificial carbon nitride (termed as f-NC) without post treatment. The f-NC template can be decomposed under high-temperature annealing, additionally, it can serve as N source to enrich the N content. Applying f-NC template, we manage the synthesis of hollow-structured highly dispersed binary FeCo-nitrogen-carbon material (termed as f-NC@FeCo-NC). Its hollow feature is confirmed by direct observation using HRTEM . Meanwhile, Fe/Co in oxidation states have been verified uniformly distributing in heavily N-doped CMs (N content ∼ 13.2 at.%). The resulted f-NC@FeCo-NC, as examined by electrochemical measurements, exhibits highly efficient performance toward oxygen reduction reaction (ORR) in alkaline medium. It respectively shows much enhanced onset and half-wave potentials of 1.01 and 0.89 V relative to the FeCo-NC that is obtained without f-NC, in contrast, 20 wt% Pt/C shows 0.95 V onset potential and 0.83 V half-wave potential. The f-NC@FeCo-NC catalyst also shows excellent Al-air battery performance when applied as cathode, which possesses a high open circuit voltage of 1.91 V and a high peak power density of 241 mW cm −2 . We believe this sacrificial f-NC can be applied as general template for the fabrication of other hollow-structured carbon-based materials for broad electrochemical applications.
Mei Guo,Xin Zhang,Tianhua Yang,Qidong Dang,Xuejin Li,Yaqun Wang,Guoxin Zhang
Aluminum-air batteries (AAB) have been expected as one promising energy technology for next-generation electrical vehicles owing to their low costs, light weights, high specific energy, environmental benignity and mechanical rechargeability. Yet currently, efficient catalytic materials for air cathodes are mostly based on expensive and scarce precious metal Pt, which have severely impeded the implantation of AAB. Herein, a series of non-precious binary FeCo-nitrogen-doped carbon (FeCo-NC) materials with heavily loaded Fe/Co species and in-situ generated interconnected carbon nanotube (CNT) were synthesized from cost-effective materials. With merits of dense active sites, largely exposed surface area, and good electron/ionic conductivity, the as-made binary FeCo-NC with optimal synthetic parameters exhibit excellent oxygen reduction reaction performance in alkaline electrolyte , rendering high onset potential of 1.05 V and half-wave potential of 0.91 V, which surpass those of Pt/C by 50 and 40 mV, respectively. Remarkably, the FeCo-NC-assembled AAB delivers an exceptional open-circuit voltage of 1.88 V and a large specific power of 188 mW cm −2 , and additionally maintains high discharge voltage of 1.70 V at the current density of 10.0 mA cm −2 . Our work renders a new type of high-performance air cathode material for AAB implantation.
Wang Yiyan,Kumar Anuj,Ma Mang,Jia Yin,Wang Yu,Zhang Ying,Zhang Guoxin,Sun Xiaoming,Yan Zifeng
Carbon materials featuring hierarchical pores and atomically dispersed metal sites are promising catalysts for energy storage and conversion applications. Herein, we developed a facile strategy to construct functional carbon materials with a fluffy peony-like structure and dense binary FeCo-N x active sites (termed as f-FeCo-CNT). By regulating the metal content in precursors, a three-dimensional (3D) interconnected conductive carbon nanotubes network was in-situ formed throughout the atomically dispersed FeCo-NC matrix during pyrolysis. Taking advantage of rich pore hierarchy and co-existence of highly active FeCo-N x sites and beneficial FeCo alloy nanoparticles, the f-FeCo-CNT material exhibited excellent bifunctional performance towards oxygen reduction reaction/oxygen evolution reactions (ORR/OER) with respect to the atomically dispersed FeCo-NC (SA-f-FeCo-NC) and commercial Pt/C+RuO 2 mixture, surpassing the SA-f-FeCo-NC with a 20 mV higher ORR half-wave potential and a 100 mV lower OER overpotential (at 10.0 mA/cm 2 ). Remarkably, the f-FeCo-CNT-assembled Zn-air battery (ZAB) possessed a maximum specific power of 195.8 mW/cm 2 , excellent rate capability, and very good cycling stability at large current density of 20.0 mA/cm 2 . This work provides a facile and feasible synthetic strategy of constructing low-cost cathode materials with excellent comprehensive ZAB performance.
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