Search

Highly effective bifunctional oxygen electrocatalysts play a key role in fuel cells (FCs), metal–oxygen batteries, and water splitting devices. In this paper, metal organic layer (MOL) derived Co/Co9S8 nanoparticles coated with N,S co-doped graphene-like carbon nanosheets were synthesized with the help of the space-confinement effect of montmorillonite (MMT). The as-prepared material shows excellent electrocatalytic activity both for oxygen reduction and oxygen evolution reactions in 0.1 M KOH solution: its ORR onset potential is 0.93 V (vs. RHE) and the limiting diffusion current density is 4.7 mA cm−2. Moreover, the retention of current for the as-prepared material is 85% after a stability test for 10 000 s for the ORR, while those of the template free catalyst and commercial Pt/C glided below 80%. Additionally, its Tafel slope is 265 mV dec−1, which is much smaller than that of the control sample, suggesting the excellent OER kinetics. The excellent catalytic activity and stability can be attributed to the relatively higher specific surface area, higher number of pyridinic-N and Co–Nx active sites, and higher graphitization degree compared to the template free catalyst. [ABSTRACT FROM AUTHOR]

In this work, FeCo/N‐doped porous carbon nanosheets (FeCo/NPC) were in‐situ synthesised as bifunctional oxygen catalyst following a sodium chloride (NaCl) template‐assisted strategy. The results show that this strategy assists in generating a 3D interconnected carbon nanosheets network with hierarchical pores and a larger specific surface area through a stencil effect. X‐ray photoelectron spectroscopy (XPS) results show that the Fe 2p3/2 and Co 2p3/2 core‐level binding energy (BE) of the FeCo/NPC catalyst exhibits a positive shift compared to monometallic catalysts, which is associated with downshifts of the d‐band position of the metal by alloying and weakening of the interaction between oxygenic species and metal surfaces, thereby improving the catalytic activity. The FeCo/NPC catalyst shows excellent electrocatalytic activity for bothoxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline solution: a high onset potential of 0.92 V (vs. RHE), only 10 mV difference of half‐wave potential comparable with commercial Pt/C (20 wt%), a high current retention of 95.7 % after stability test of 20000 s for ORR and a potential of 1.68 V (vs. RHE) for OER at 10 mA ⋅ cm−2. The high catalytic performance of the FeCo/NPC catalyst and the simplicity of the synthesis method provide a possibility for its practical application in metal‐air batteries. Connect the dots: FeCo/N‐doped 3D interconnected porous carbon (FeCo/NPC) nanosheets are synthesized following a NaCl template‐assisted strategy in a one pot approach. The resulting FeCo/NPC electrocatalyst shows excellent catalytic activity and stability for both, the oxygen evolution reaction and the oxygen reduction reaction, demonstrating its promising potential for applications in metal‐air batteries. [ABSTRACT FROM AUTHOR]

We described a process of the preparation of N, P co-doped hierarchical porous carbon by one-step pyrolysis of the chitosan/phytic acid (CS/PA) precursor without extra activation processes, and the nitrogen and phosphorus were successfully incorporated into the carbon framework. Experimentally, the best performance was identified with NPC-1000 which possessed the highest BET specific surface area of 1117.2 m 2 g −1 . This NPC-1000 showed a half-wave potential of 50 mV difference with commercial Pt/C, better tolerance to methanol and a superior stability comparable to commercial Pt/C catalyst. The results suggest that it is a simple, feasible, and economical route to synthesis of hierarchical porous carbon which can be used as metal-free catalysts for oxygen reduction. [ABSTRACT FROM AUTHOR]

In this work, for the first time, MgFe 2 O 4 (MFO) is used to stabilize the N-doped 3D carbon nanosheets supported platinum catalysts (Pt/MFO/NPC). The spherical MFO nanoparticles are randomly dispersed on the surface of the 3D carbon nanosheets, with Pt particles uniformly distributed on them. The Pt/MFO/NPC catalyst possesses excellent stability and methanol tolerance in alkaline solution. The current retention reaches 87.0% after 20,000 s of stability test, which is significantly higher than that of commercial Pt/C (46.9%). In addition, the onset potential (E onset) and half-wave potential (E 1/2) values of Pt/MFO/NPC are larger than that of the commercial contrast, implying the improved kinetics of the Oxygen reduction reaction (ORR). The excellent catalytic activity and stability of Pt/MFO/NPC can be attributed to the combined effect of N-doping and strong metal-support interaction (SMSI) between MFO and Pt. Image 1 • 3D carbon nanosheets were prepared through urea and sodium metasilicate nonahydrate as dual template. • MgFe 2 O 4 was used to stabilize the N-doped 3D carbon nanosheets supported platinum catalysts. • A strong metal-support interaction between MFO and Pt was investigated in detail. • The Pt/MFO/NPC catalyst possesses excellent stability and methanol tolerance in alkaline solution towards ORR. [ABSTRACT FROM AUTHOR]

Abstract The design of porous carbon frameworks with high-density distributions of dopant sites, especially those derived from renewable biomaterials, is highly desirable to improve the activity of nonprecious porous carbon catalysts for oxygen reduction reaction (ORR). In this paper, we prepared N, P-doped hierarchical porous carbon catalysts via a direct pyrolysis of a gelatin/phytic acid supermolecular aggregate without extra activation processes. The optimal catalyst materials (NPC1000) showed not only the highest N and P contents but also the highest specific surface area, total pore volume and mesoporous pore volume, which are also higher than those of the contrast sample prepared with a chitosan/phytic acid supermolecular aggregate. Thus, the sample NPC1000 had the best electrocatalytic activity compared with the Pt/C catalyst, which was nearly a direct four-electron reaction. The sample also had higher stability and methanol tolerance than Pt/C. This work provides a simple, economical and environmentally friendly method to prepare nonprecious porous carbon catalysts with the desired properties. Graphical abstract Image 1 Highlights • Biological materials gelatin and phytic acid are used as raw materials. • Porous carbon framework featuring sheets own large surface area and pore volume. • The one-step pyrolysis method is facile without activation. • The high ORR activity is attributed to high N and P content and unique structure. • Especially, the mesoporosity play a crucial role in boosting the ORR performance. [ABSTRACT FROM AUTHOR]

Onion-derived nitrogen, sulfur self-doped nanoporous carbon spheres (NSC) as efficient metal-free electrocatalyst were synthesized via a facile hydrothermal and subsequent pyrolysis process. The typical NSC with a high BET specific surface area of 1558 m 2 g −1 , contains 6.23 at.% N and 0.36 at.% S, and possesses high concentration of pyridinic and graphitic nitrogen species. Experimentally, the best performance was the NSC-A2 which showed excellent catalytic activity to oxygen reduction reaction via a 4 electron mechanism with an onset potential of 0.88 V (vs. RHE), and a superior stability comparable to commercial Pt/C catalyst. The high electrocatalytic activity is attributed to not only the synergistic effect of N and S dual doping in carbon and the sufficient active sites, but also its high BET specific surface area and suitable microporous structure. The results demonstrate that it is a simple and scalable approach for preparing efficient and low-cost carbon-based electrocatalysts for oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

Developing catalysts with high bi-functional electrocatalytic activity for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for the fuel cells and metal-air batteries because of the sluggish kinetics of oxygen electrochemical reaction. Herein, we prepared a porous and well dispersed spinel MnCo 2 O 4 (MCO) catalyst through a facile solvothermal method followed by a calcination process. CH 3 COONH 4 used in solvothermal process played an important role in control of the size and morphology of MCO. The as-prepared MCO submicrospheres feature a porous structure and a high specific surface area. Tested by the rotating ring disk electrode (RRDE) technique, the sample MCO-10 and MCO-5 shows best catalytic towards ORR and OER, respectively. In particular, MCO-10 exhibits a high diffusion limiting current density (5 mA cm −2 ) and a better stability comparable to commercial Pt/C (20 wt% Pt on carbon) catalyst. [ABSTRACT FROM AUTHOR]