Cu-based electrode material for controlled selective electrooxidation of tetrahydroisoquinolines†

Abstract

The oxygen evolution reaction with its high energy barrier on the anode during water electrolysis is the main factor limiting its large-scale application. A viable strategy is to explore anode substitution reactions to replace the oxygen evolution reaction in water electrolysis. In this study, the selective electrooxidation of tetrahydroisoquinoline (THIQ) was demonstrated on a specially designed and prepared Cu₂S electrode, which was coupled with the hydrogen evolution reaction. The process exhibits high selectivity of over 90% for the micro-electrooxidation of THIQ to dihydroisoquinoline (DHIQ). The high selectivity is caused by the fact that the oxygen evolution reaction (OER) blocks the transformation from DHIQs to isoquinolines (IQs) and by the excellent performance of the designed catalytic electrode made from a ds-region material. An in situ Raman and XPS investigation confirmed that the main active substance is a Cu(III) species, which was in situ derived on the surface of Cu₂S. Based on the results of DFT calculations, a possible catalytic reaction mechanism of Cu-based catalysts for the selective micro-electrooxidation of THIQs was proposed.