He obtained his Bachelor of Science degree in 1975 followed by a PhD in 1978 from the University of Leeds[7][8] supervised by Geoff Sykes.
[9] After his PhD, Armstrong carried out postdoctoral research with Peter Kroneck (Konstanz), Ralph Wilkins (New Mexico), Helmut Beinert (Madison), and Allen Hill (Oxford).
[citation needed] In 1983 he was awarded a Royal Society University Research Fellowship which he held in Oxford until 1989, when he joined the Chemistry Faculty at the University of California, Irvine.
His interests are in biological redox chemistry, in particular the application of dynamic electrochemical techniques in studies of complex electron-transfer and catalytic reactions in proteins (protein film voltammetry), and most recently the mechanisms and exploitation of biological hydrogen cycling.
He was the president of the Society of Biological Inorganic Chemistry (SBIC) from 2004 to 2006.