Facile Method To Study Catalytic Oxygen Evolution Using a Dissolved Oxygen Optical Probe: An Undergraduate Chemistry Laboratory To Appreciate Artificial Photosynthesis

Abstract

Artificial photosynthesis (AP) is a synthetic chemical process that replicates natural photosynthesis to mass produce hydrogen as a clean fuel from sunlight-driven water splitting (2H2O → O2 + H2). In both natural and artificial photosynthesis, an oxygen-evolving catalyst (OEC) is needed to catalyze oxygen production from water (2H2O → O2 + 4H+ + 4e–). Herein, we present a simple undergraduate laboratory experiment for monitoring the catalytic oxygen-evolution reaction using a dissolved oxygen optical probe, a luminescent probe that can continuously measure the concentration of dissolved oxygen in aqueous solutions. The laboratory experiment consists of two parts. First, students identify and evaluate the necessary criteria for an active molecular O2-evolving catalyst. Second, students use a kinetic protocol based on the method of initial rates to derive an empirical rate law expression and calculate the turnover frequency and rate constant for a benchmark OEC, [RuII(tpy)(bpy)(H2O)]2+ (tpy is 2,2′:6′,2″-t...