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dataframe - How to initialize empty data frame (lot of columns at the same time) in R

I found how to initialize an empty data frame with 3 or 4 dimensions. It's like

df <- data.frame(Date=as.Date(character()),
             File=character(), 
             User=numeric(), 
             stringsAsFactors=FALSE)

However, What's the most effective way to initialize an empty data.frame with a lot of column names. like

mynames <- paste("hello", c(1:10000))

The wrong way I tried is:

df <- data.frame(mynames=numeric())

Thanks a lot beforehand

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Maybe this -

df <- data.frame(matrix(ncol = 10000, nrow = 0))
colnames(df) <- paste0("hello", c(1:10000))

And @joran's suggestion - df <- setNames(data.frame(matrix(ncol = 10000, nrow = 0)),paste0("hello", c(1:10000)))


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