Efficient photocatalytic hydrogen evolution without an electron mediator using a simple electron donor–acceptor dyad

Abstract

A highly efficient photocatalytic hydrogen evolution system without an electron mediator such as methyl viologen (MV²⁺) has been constructed using 9-mesityl-10-methylacridinium ion (Acr⁺–Mes), poly(N-vinyl-2-pyrrolidone)-protected platinum nanoclusters (Pt–PVP) and NADH (β-nicotinamide adenine dinucleotide, reduced form) as the photocatalyst, hydrogen evolution catalyst and electron donor, respectively. The photocatalyst (Acr⁺–Mes) undergoes photoinduced electron transfer (ET) from the Mes moiety to the singlet excited state of the Acr⁺ moiety to produce an extremely long-lived ET state, which is capable of oxidizing NADH and reducing Pt–PVP, leading to efficient hydrogen evolution. The hydrogen evolution efficiency is 300 times higher than that in the presence of MV²⁺ because of the much faster reduction rate of Pt–PVP by Acr^˙–Mes compared with that by MV^˙+. When the electron donor (NADH) is replaced by ethanol in the presence of an alcohol dehydrogenase (ADH), NADH is regenerated during the photocatalytic hydrogen evolution.