The design of high-performance oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) dual-functional catalysts is not only important for the further applications of zinc-air batteries (ZABs) but also a major challenge in the field of energy conversion. The cheap 1,2,4-triazole (1,2,4-TZ) can be decomposed easily by heat, making it a high research value in carbon catalysts derived from metal-organic frameworks (MOFs). Here, Co 4 N particles encapsulated at the top of N -doped carbon nanotubes (Co 4 N@NCNTs) were conveniently prepared by 1,2,4-TZ-assisted pyrolysis of Co-MOF-74 for the first time. Owing to the excellent activity of Co 4 N particles and the highly graphitized N -doped carbon nanotubes (NCNTs), Co 4 N@NCNTs obtained at 900 °C (Co 4 N@NCNT-900) exhibited astonishing catalytic performance in both ORR and OER, and high reversible oxygen bifunctional activity (ΔE = 0.685 V). Moreover, Co 4 N@NCNT-900 displayed a larger discharge power density (122 mW cm −2 ), a better specific capacity (811.8 mAh g −1 ), and more excellent durability during the ZAB test, implying that Co 4 N@NCNT-900 can act as a bifunctional high active catalyst in ZABs.
Designing high-efficiency electrocatalysts for glucose concentration detection plays a pivotal role in developing various non-enzymatic glucose detection devices. Herein, we have successfully designed and synthesized various cobalt nitrides (Co 4 N) by using different weak bases ( i.e. hexamethylenetetramine (HMT), urea, and ammonium hydroxide (AH)) through nitridation treatment in ammonia (NH 3 ) atmosphere. Physical characterization results demonstrate that Co 4 N-NSs (nanosheets) with vast meso/macropores and large BET surface are successfully constructed once adding carbon paper and HMT into precursors. As the synergistic effect of metallic character of Co 4 N phase , excellent electroconductibility of pyrolytic carbon , and large surface area , Co 4 N-NSs surfaces can form more Co 4+ active sites in electrochemical reaction processes. Meanwhile, the abundant meso/macroporous structures constructed in Co 4 N-NSs further promoted its mass transfer ability. Benefitting from the above mentioned advantages, Co 4 N-NSs therefore exhibit more excellent glucose oxidation ability than another three control samples ( i.e. Co 4 N-HMT, Co 4 N-Urea and Co 4 N-AH). When used for glucose detection, the optimal Co 4 N-NSs display excellent detection parameters as well, such as: a wide linear range of 0.6–10.0 mM, a large sensitivity of 1137.2 uA cm −2 mM −1 glucose, a low detection limit of 0.1 µM, a small response time of 1.7 s, good reproducibility and stability, and the excellent anti-interference to other electroactive molecules and Cl − . Upon utilized for measuring glucose concentrations in human blood serum samples, the detection results on Co 4 N-NSs are accurate and satisfying as well. This work opens a new possibility for boosting electrochemical catalysis abilities of Co 4 N samples by the structure design.
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