Carbon-metal composites are promising multifunctional electrocatalysts , but it is still challenging to prepare carbon-metal composites with tunable structure and strong metal-carbon interactions. Here, we present a unique gas-foaming assembly strategy to prepare cytosine-Co chelate derived Co and N codoped carbon nanotube (Co-NCNT). The structure for Co-NCNTs could be easily controlled by regulating cytosine-Co coordination or the carbonization temperature. The optimal Co-NCNT possesses homogeneous distributed NCNTs (10 nm), CoO x (5 nm) and CoN x moieties to synergistically boost electrochemical processes, and offer mesoporous nanosheet architecture to guarantee fast mass migrate and electron transfer . As a result, Co-NCNT shows remarkable ORR performance (onset potential of 0.93 V in 0.1 M KOH electrolyte) along with significant OER and HER activity. More important, it was found that CoN x moieties are responsible for the remarkable electrocatalytic activity in Co-NCNTs, because CoN x could alter active center, enhance metal-carbon synergy, decrease interfacial resistance and reinforce the strength of composites. Therefore, this paper not just demonstrates an advanced multi-functional electrocatalyst, but could also give deep understanding on the designing of multifunctional electrocatalysts.
The nonradical pathway selectively oxidizes pollutants with less interference from environmental factors, which can effectively improve the environmental suitability of peroxymonosulfate (PMS) activation. Herein, a Co-doped nanotubular carbon nitride catalyst (Co-CNNT) based on CoN x sites was constructed for stable and efficient PMS activation with a better specific surface area, number of CoN x sites, and electron transfer capability than Co-doped lamellar carbon nitride catalyst (Co-CN). Co-CNNT improved PMS utilization efficiency (∼50%) and enhanced the contribution of the electron transfer pathway to tetracycline (TET) degradation. The enhanced ability of Co-CNNT to adsorb PMS leads to Co-CNNT–PMS* generated by PMS at the CoN x site, which raises the Co-CNNT surface potential and allows PMS to be activated in a manner that captured electrons. Thus, the Co-CNNT/PMS system could effectively destroy electron-rich or low-potential pollutants within 24 min. The stronger environmental adaptability allows it to maintain catalytic activity in complex aqueous matrices, achieving effective oxidation of diluted tetracycline-based pharmaceutical wastewater. This paper reveals the effects of carbon nitride morphology control strategies on the properties of CoN x active sites and PMS activation mechanisms, providing new insights into the induction of nonradical PMS activation pathways.
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