Predicting the efficiency of a photocatalytic reaction

Abstract

Photocatalytic systems that use the absorbed light to induce redox reaction find applicability in a wide range of technologies. Today the performance of such systems is often reported in terms of the quantum efficiency. The quantum efficiency, however, strongly depends on the used excitation source. In practice, the performance of photocatalytic systems is often studied using high energy excitation sources to ensure good photon absorption. As a result, high efficiencies are reported which could lead to misleading information when considering the available light many of these technologies rely on, namely the sun. In this work we model the basic steps encountered in photocatalytic reactions in order to predict the performance as a function of the photocatalyst material and the incident light. By separately assessing the photon absorption, carrier kinetics and incident light before calculating the efficiency, the model provides a highly adaptive tool to assess and compare the photocatalytic performance for different photocatalyst materials and light sources. Our model shows to effectively predict the product formation rates and performance limitations of photocatalytic water splitting. Furthermore, it underlines the fact that large apparent quantum efficiencies do not necessarily indicate high photocatalytic efficiencies.