A bifunctional nanozyme of carbon dots-mediated Co9S8 formation

N,S co-doped porous carbon with Co9S8 prepared with a Co-FF-derived Co3O4 template: a bi-functional electrocatalyst for rechargeable zinc-air batteries

To achieve broad commercialization of rechargeable metal-air batteries, the development of non-precious metal-based bi-functional oxygen electrocatalysts is critical. In this study, we prepared N,S co-doped porous carbon materials containing Co9S8 nanoparticles (Co9S8/NSC) through a one-step pyrolysis process. The process involved the pyrolysis of a polydopamine (PDA) coated Co-formic acid framework (Co-FF) derived Co3O4 and thiourea. The improved catalyst Co9S8/NSC-1 exhibited satisfactory long-term durability and superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity, the half-wave potential (E1/2) of the ORR reached 0.83 V, and the OER overpotential at 10 mA cm-2 (η10) was 300 mV. The zinc-air battery (ZAB) based on Co9S8/NSC-1 assembly had a maximum power density of 102.0 mW cm-2 and the cycle life reached 500 cycles. The material preparation method was simple, environmentally friendly and inexpensive, providing a feasible strategy for the development of non-precious metal-based electrocatalysts.

Carbon-Based Enzyme Mimetics for Electrochemical Biosensing

Natural enzymes are used as special reagents for the preparation of electrochemical (bio)sensors due to their ability to catalyze processes, improving the selectivity of detection. However, some drawbacks, such as denaturation in harsh experimental conditions and their rapid de- gradation, as well as the high cost and difficulties in recycling them, restrict their practical applications. Nowadays, the use of artificial enzymes, mostly based on nanomaterials, mimicking the functions of natural products, has been growing. These so-called nanozymes present several advantages over natural enzymes, such as enhanced stability, low cost, easy production, and rapid activity. These outstanding features are responsible for their widespread use in areas such as catalysis, energy, imaging, sensing, or biomedicine. These materials can be divided into two main groups: metal and carbon-based nanozymes. The latter provides additional advantages compared to metal nanozymes, i.e., stable and tuneable activity and good biocompatibility, mimicking enzyme activities such as those of peroxidase, catalase, oxidase, superoxide dismutase, nuclease, or phosphatase. In this review article, we have focused on the use of carbon-based nanozymes for the preparation of electrochemical (bio)sensors. The main features of the most recent applications have been revised and illustrated with examples selected from the literature over the last four years (since 2020).