Effect of catalyst type on the type and size of nano-diamond synthesized by chlorine gas etching of Ti₃C₂ MXene under ambient pressure

Recently, we have successfully achieved the atmospheric pressure catalytic synthesis of nanodiamonds by applying high stress to Ti₃C₂/Ni composite and then performing chlorine gas etching at atmospheric pressure. In this work, we chose three different catalysts (Fe, Co and Ni), with Ti₃C₂ as the precursor, aiming to investigate the effect of catalyst type on the synthesis of NDs. The results show that all three catalysts can catalyze the synthesis of NDs and that the crystal type and plasticity of the catalysts may have an important effect on the type and size of the resulting ND. When Fe and Ni were used as catalysts, the percentage of C-type NDs obtained was higher than that of C-type NDs catalyzed by Co (hexagonal close-packed crystal structure) due to its face-centered cubic crystal structure. In contrast, more H-type NDs were catalytically synthesized when Co (hexagonal close-packed crystal structure) was used as the catalyst. In addition, the number of small-size NDs (< 10 nm) catalytically synthesized by Co was significantly more than that catalytically synthesized by Fe and Ni, this may be caused by the poor plasticity of Co with a hexagonal close-packed crystal structure compared to Fe and Ni with a face-centered cubic crystal structure.