Submillimeter single-crystal graphene on copper foils was synthesized by chemical vapor deposition. The influence of cooling rate on hydrogen etching of graphene has been studied by using three different types of cooling method. Methane has been introduced during the cooling process to reduce the etching effect and the etching mechanism has been discussed. The results show that fast cooling by just opening the furnace after graphene growth has the lowest etching effect

while the furnace cooling results in intermediate level of etching

and the slow cooling has the most serious etching. The etching damage reduced after methane is introduced during the cooling process. The crystal quality of open furnace cooling graphene was highly increased

while for the furnace cooling graphene it increased slightly

for the slow cooling graphene

the crystal quality decreased.