what is the surface of neptune made from
Mainly hydrogen and helium, along with water, methane, ammonia, hydrocarbons and nitrogen
Neptune
Like Jupiter and Saturn, Neptune's atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, though it contains a higher proportion of "ices" such as water, ammonia and methane. 
wiki:22147477
Neptune [SEP] Introduction
However, similar to Uranus, its interior is primarily composed of ices and rock; Uranus and Neptune are normally considered "ice giants" to emphasise this distinction. Traces of methane in the outermost regions in part account for the planet's blue appearance.