Impact of hole scavengers on photocatalytic reduction of nitrobenzene using cadmium sulfide quantum dots

One key factor that affects the reaction yield and selectivity of nanoparticle-catalyzed photochemical reactions is the type of hole scavengers. In this work, we examine the effect of hole scavengers in photoreduction of nitrobenzene catalyzed by cadmium sulfide quantum dots. We discover that the hole scavengers can determine the reduction pathway as well as the final product. Specifically, when methanol is the solvent and the sole hole scavenger, or when it is used in conjunction with ascorbic acid, ammonium formate, mercaptopropionic acid, or sodium borohydride, the reaction follows a direct reduction pathway. In contrast, with methanol and sodium sulfite, the reaction proceeds via a coupling route. Some hole scavengers directly participate in the redox reaction of intermediates. This study demonstrates that the type of hole scavenger can alter the reaction pathways and determine the reaction outcome and should be chosen with careful consideration.