Aligned carbon nanotube array functionalization for enhanced atomic layer deposition of platinum electrocatalysts

► Surface functionalization of CNT surfaces influences the growth of Pt by ALD inside aligned CNT arrays. ► Pt density and uniformity inside arrays depends strongly on the gasses used for functionalization. ► Ar plasma blocks nucleation, O2 plasma and trimethylaluminum treatments enhance uniformity. ► Generation/reduction of oxygen rich defect sites is the key to promote/block Pt ALD nucleation.