Bifunctional catalytic and capacitive properties of CoC and CoC/Zn derived from cobalt complex pyrolysis

Abstract

This research evaluates the use of metal nanoparticles, produced from the pyrolysis of metal–organic frameworks, as catalysts for breaking down organic pollutants. The study specifically examines CoC and CoC/Zn nano-catalysts, which were synthesized, characterized, and tested against pollutants like p-nitrophenol (PNP) and methyl orange (MO) using sodium borohydride. SEM analysis showed that the nanoparticles ranged in size from 50 to 200 nm, while TEM revealed smaller sizes from 20 to 100 nm. EDX analysis confirmed zinc’s presence in CoC/Zn, and XPS analysis detected various elements, including C, N, O, Cl, Co, and Zn in CoC/Zn, with the absence of Zn and presence of K in CoC. Additional tests like EDAX and XRD confirmed the presence of Co and Zn in the samples. During the pyrolysis, graphite was formed, as indicated by Raman spectroscopy. BET analysis showed that Co/C had a surface area of 100 m²/g, which was significantly higher than CoC/Zn, attributed to the use of K₂EDTA during Co/C’s synthesis. In degradation tests, CoC outperformed CoC/Zn, with first-order rate constants of 0.128 min⁻¹ for PNP and 0.425 min⁻¹ for MO, showing higher catalytic efficiency and durability—lasting 18 cycles for PNP and 34 cycles for MO. Although CoC/Zn had lower performance, it was noted for its efficiency. In terms of energy storage, CoC/Zn and CoC displayed specific capacitance values of 470 F/g and 560 F/g, respectively, and showed high durability by retaining about 93.46% of their original capacitance after 2300 cycles. These findings underscore the potential of CoC as an effective, durable catalyst for environmental cleanup and both materials as viable, cost-effective options for energy storage.