High yield and wide lateral size growth of α-Mo2C: exploring the boundaries of CVD growth of bare MXene analogues.

Synthesis of Mo2C bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for Mo2C MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration. We report a facile modification of their typical CVD growth protocol and show its influence on the Mo2C synthesis, with growth times spanning up to 3 h. Specifically, prior to initiating the CVD growth process, we introduced a holding step in temperature at 1095 °C. This proved to be beneficial in increasing the Mo concentration on the liquid Cu growth surface. We achieved an average Mo2C crystals coverage of approximately 50% of the growth substrate area, increased tendency of coalescence and merging of individual flakes, and lateral flake sizes up to 170µm wide. To gain deeper understanding into their CVD growth behavior, we conducted a systematic investigation of the effect of several factors, including (i) a holding step time on Mo diffusion rate through molten Cu, (ii) the Cu foil thickness over the Mo foil, and (iii) the CVD growth time. Phase, chemical and microstructural characterization by x-ray diffraction, x-ray photon spectroscopy, SEM and scanning/transmission electron microscopy revealed that the grown crystals are single phaseα-Mo2C. Furthermore, insights gained from this study sheds light on crucial factors and inherent limitations that are essential to consider and may help guide future research progress in CVD growth of bare MXenes.

Graphene from discharged dry cell battery electrodes.

Utilization of extracted graphite rods from discharged dry cell batteries for synthesis of graphene oxide / graphene serves two purposes, one is waste management which supports environmental safety and the second is low cost production of graphene oxide / graphene which are highly promising 2D materials in various fields of research. In the present work, a sustainable feasibility for the synthesis of graphene oxide / graphene from graphite rods of waste dry cell batteries is demonstrated. The graphite rods separated from the waste dry cell batteries were subjected to electrochemical exfoliation (ECE) in an acidic media. The graphene oxide (GO) obtained from this method was subjected to reduction heat treatment under argon atmosphere at suitable temperature and time period. Finally, the reduced graphene oxide (rGO) i.e., graphene was characterized using XRD, FTIR, Raman Spectroscopy, TGA, BET, SEM and TEM. The few layer graphene structure is supposed to be less defective in comparison to similar exfoliation techniques due to less oxygen-functional groups associated with the intermediate graphene oxide.