Amine-Functionalized Metal-Free Nanocarbon to Boost Selective CO2 Electroreduction to CO in a Flow Cell.

Highly efficient electrochemical CO2-to-CO conversion is a promising approach for achieving carbon neutrality. While nonmetallic carbon electrocatalysts have shown potential for CO2-to-CO utilization in H-type cells, achieving efficient conversion in flow cells at an industrial scale remains challenging. In this study, we present a cost-effective synthesis strategy for preparing ultrathin 2D carbon nanosheet catalysts through simple amine functionalization. The optimized catalyst, NCNs-2.5, demonstrates exceptional CO selectivity with a maximum Faradaic efficiency of 98% and achieves a high current density of 55 mA cm-2 in a flow cell. Furthermore, the catalyst exhibits excellent long-term stability, operating continuously for 50 h while maintaining a CO selectivity above 90%. The superior catalytic activity of NCNs-2.5 is attributed to the presence of amine-N active sites within the carbon lattice structure. This work establishes a foundation for the rational design of cost-effective nonmetallic carbon catalysts as sustainable alternatives to metals in energy conversion systems.

Surface state engineering of carbon dot/carbon nanotube heterojunctions for boosting oxygen reduction performance.

Platinum-based (Pt) catalysts are the most common commercial catalysts for oxygen reduction reactions (ORR). Unfortunately, their high price, scarcity and poor durability hinder their further development. Therefore, the development of effective and economical ORR electrocatalysts has received increasing attention. Here, carbon dots (CDs) enriched in amino functional groups were successfully loaded onto carbon nanotubes (CNTs) with a large surface area and helical structure through a surface state engineering strategy. The resulting composites (CD/CNTs) are 0D/1D nano heterojunction structures. The CD/CNTs showed superior ORR activity compared with CNTs and CDs (Eoneset = 0.95 V, E1/2 = 0.81 V and limiting current density = 4.74 mA cm-2). In addition, the stability of CD/CNTs in an alkaline medium was up to 30000 s. The excellent ORR performance of CD/CNTs can be attributed to the dominant role of amino-N, the synergistic effect of heterojunctions formed by CDs and CNTs, and the high Lewis basicity. The composite electrocatalyst synthesized by the CD-regulated CNT strategy is expected to be a reliable cathode candidate for future energy conversion devices.