Cu has shown an advantage in growing monolayer graphene due to the very low C solubility and surface-mediated self-limiting growth, which hinders the growth of multilayer graphene. This work reports an unconventional penetration etching/growth of graphene adlayers tuned by oxygen beyond the self-limiting growth, supported by the C isotope labeling results. The effect of oxygen is nonmonotonic, i.e., with the increase of oxygen, graphene adlayers are etched without damaging the top layer, then shift to growth, and finally, all layers are etched. In addition, the reaction did not seem to reach equilibrium in the time range of the experiment but continued as if oxygen was increasing with respect to time. An oxygen-assisted exchange penetration model is proposed to interpret the growth mechanism. Oxygen etches the top shield layer, which is simultaneously healed by consuming the C species around adlayers and results in adlayer decomposition due to the break of equilibrium. Additionally, oxygen assists penetration of C from the gaseous agents into the shield layer for adlayer growth. The domination of one over the other depends on the concentration of oxygen, resulting in overall etching or growth. Finally, the synthesis of large-area monolayer and bilayer graphene films with good uniformity is demonstrated.

TiNb2O7 (TNO) compound has been pursued tremendously due to its high theoretical capacity, high potential, and excellent cycle stability. Unfortunately, an intrinsic low electronic and ionic conductivity feature has restricted its broad applications in electrochemical energy storage fields. Two-dimensional (2D) nanostructures can effectively shorten Li-ion transport path and enhance charge transfer. Here, hierarchical structure TNO was constructed by using ethanol and acetic acid as particularly important organic chemicals of basic raw materials via a simple solvothermal reaction. Ethanol was found to play a critical role in the formation of 2D sheet structure. Meantime, reduced graphene oxide nanosheets can effectively improve electronic conductivity. As-obtained TiNb2O7 were wrapped further by graphene oxide nanosheets through a flocculation process. Their unique structure is beneficial to the final electrochemical performance. This study not only provides a general approach for the design of novel 2D nanomaterials wrapped by graphene because of the advantage of esterification reaction and flocculation reaction, but also improves the electronic and ionic conductivity simultaneously.