ORR Activity and Stability of Co-N/C Catalysts Based on Silicon Carbide Derived Carbon and the Impact of Loading in Acidic Media

Abstract

A simple and facile synthesis method was used to produce two Co-N/C type oxygen reduction reaction (ORR) catalysts. The materials were initially characterized by utilizing a variety of physical methods. Most importantly, the XPS analysis revealed high amounts of pyridinic nitrogen and CoN x species in the case of both studied Co-N/C catalysts. The electrochemical characterization showed that both of the synthesized Co-N/C catalysts have a high ORR activity in acidic media, displaying a half-wave potential of 0.70 V vs RHE. Additionally, the effect of varying the catalyst loading was studied and it was found that increasing the catalyst loading from 0.1 to 1.8 mg cm −2 significantly improved the ORR activity and the electron transfer number. Finally, several catalysts were subjected to a week-long stability test in order to establish their activity degradation rates. It was found that increased degradation rates of the Co-N/C catalysts were established at decreased catalyst loadings.

Establishing reactivity descriptors for platinum group metal (PGM)-free Fe–N–C catalysts for PEM fuel cells

“…The general trend of increased peroxide formation with decreased catalyst loading is observed, in accordance with previous reports on both PGM-free and PGM-based catalysts. [96][97][98][99] Low catalyst loadings imply thin layers, which increases the probability of the formed peroxide molecule to escape the active layer before it can re-adsorb on another active site. Thick layers, in contrast, increase the probability of peroxide re-adsorption on a same or a different active site during its diffusion from the inner part of the active layer towards the bulk electrolyte.…”

Structural Modulation of Co Catalyzed Carbon Nanotubes with Cu–Co Bimetal Active Center to Inspire Oxygen Reduction Reaction

“…After Cu doping, the content of Co slightly decreased, which indicated the partly substitution of Co with Cu. In SI Figure S2a, three types of peaks at 778.39, 779.62, and 781.05 eV in high resolution spectra of Co could been obtained in all Co@NCNTs, which correspond to metallic Co, Co–N x –C y and Co–N x , respectively. , As shown in Figure a, the content of Co on surface dramatically decreased from 600 °C (5.25%) to 700 °C (2.56%). − When the temperature increased further from 700 to 800 °C, the content of Co kept stable (2.56% and 2.82%, respectively). Experiment data revealed that the thicker and longer nanotubes were grown on the surface of Co nanoparticles which lead to the decreasing of Co on surface.…”

“…As shown of linear sweep voltammetry (LSV) curves in Figure d, there was a significantly better ORR activity of Co@NCNT-700, which indicated much more positive onset potential 0.928 V (vs RHE) and half-wave potential 0.826 V (vs RHE) compared with Co@NCNT-600 (0.787 V vs RHE and 0.898 V vs RHE) and Co@NCNT-800 (0.802 V vs RHE and 0.91 V vs RHE). The better ORR activity of Co@NCNT-700 would ascribe to the largest specific area, higher degree of graphitization and especially the highest content of Co–N x with evenly distribution. , …”

“…The better ORR activity of Co@NCNT-700 would ascribe to the largest specific area, higher degree of graphitization and especially the highest content of Co−N x with evenly distribution. 33,36 To further optimize the performance of the Co@NCNT-700, Cu is introduced to synthesis bimetal/NCNT nanohybrids. To avoid the metal aggregation, the Co@NCNT-700 is dipped into copper salt solution for 30 min and then heat up to 300 °C to achieve a firmly binding of Cu with carbon substrate.…”

“…In order to further explore the practically application of CuCo@NCNT-700 in practical energy equipment, a homemade Zn–air battery was fabricated by 6 M KOH electrolyte, a zinc plate anode and CuCo@NCNT-700 loaded carbon cloth as air cathode (Figure a). , For comparison, Pt/C was utilized as the rechargeable noble metal air cathode in the control battery. The structure of Zn–air battery schematically shown in Figure a.…”