Variable-temperature, 1H NMR study of hydrogen chemisorption on EuroPt-1

Abstract

A specially constructed, large-sample ¹H NMR probe has been used in the study of hydrogen adsorption on EuroPt-1. Quantitative spectroscopy has shown that the support is highly hydroxylated following reduction and evacuation. No intensity which could be associated with hydrogen spillover is observed in the NMR spectrum following hydrogen adsorption. Two Knight shifted peaks are detected, assigned to hydrogen chemisorbed to the platinum surface (β) and hydrogen chemisorbed at the metal/support interface (γ). The coverage and pressure dependency of the resonant frequency of peak β has been successfully described by the rapid exchange between two adsorbed states, strongly and weakly bound, and hydrogen in the gas phase, each having a resonant frequency that is coverage and temperature-independent in the range 195–333 K. By 195 K, the fast exchange between the adsorbed and gas phases has been ‘frozen out’, although fast exchange between the two adsorbed species persists.