Multiple catalytic sites of Fe-Nx and Fe-N-C single atoms embedded N-doped carbon heterostructures for high-efficiency removal of malachite green

Abstract A series of Fe-N-C single atom catalysts embedded within the carbon nitride network (Fe-N-C/CNx) were developed to effectively degrade a commonly used organic dye, malachite green (MG). Fe-N-C/CNx catalysts were achieved by pyrolyzing the hybrid of polypyrrole (PPy) and melamine–cyanuric acid complex (MCA) containing trace Fe3+ (Fe/PPy@MCA) at different temperatures. Given the structural change of polymeric networks and nitridation of Fe3+, the mesoporous Fe-N-C/CNx hybrids comprise multiple components, including Fe-N-C, Fe4N, and CNx species, which show enhanced photocatalytic performance toward MG by integrating the high catalytic ability of Fe components and efficient visible-light harvest of CNx network. Notably, the Fe-N-C/CNx-700 hybrid obtained at 700 °C exhibits the high removal efficiency of 92.1% toward MG under visible light, with good reproducibility and stability. The biotoxicity of degraded products was further investigated by antibacterial experiment and plant growth effect. This work provides new insights into the development of efficient photocatalysts of nanohybrids for treating organic dyes.