Optimization of Processing Parameters for High-Quality Monolayer Graphene

Commercial Copper foils typically exhibit surface roughness and non-uniform nucleation, which make it difficult to reproducibly grow high-quality monolayer-dominant graphene by atmospheric pressure chemical vapor deposition （APCVD）. In this paper, a pretreatment and process optimization strategy for APCVD growth of high-quality graphene on commercial Cu foils is established, aimed at providing a reliable substrate preparation route for subsequent device and electrochemical applications, including graphene transparent electrodes in solar cells and other photovoltaic devices. A phosphoric acid/PE4300 electropolishing system is combined with mixed-acid cleaning in 3.5% HCl and 3% HNO₃ to optimize polishing time and the reuse number of the electrolyte. On this basis, the effects of growth temperature, annealing time, and growth time on the graphene structure and surface chemical state are systematically investigated using SEM, Raman spectroscopy, and XPS. The results show that: after 30 min of electropolishing followed by mixed-acid cleaning, the Cu surface becomes the flattest and most compact, and the polishing solution can be stably reused about 3~5 times. Under optimized APCVD conditions of 1080 ℃ with a 30 min anneal and 50 min growth, the resulting graphene exhibits a weak D band and I_G/I_2D < 0.5, indicating monolayer-dominant films with markedly improved continuity and uniformity. These results demonstrate that combining phosphoric acid/PE4300 electropolishing with mixed-acid cleaning and coordinated optimization of growth parameters significantly enhances the structural integrity and layer-number uniformity of APCVD graphene on commercial Cu foils, providing a stable and reproducible process route for graphene transparent electrodes in solar cells and related electrochemical applications.