Determining the sequence of charge transport events and their roles on the limit of quantum efficiency of photocatalytic hydrogen production

Quantum efficiency (QE) is a defining parameter to rank the effi-ciency of a photocatalyst. The QE is governed by the kinetics of recombination and transfer processes of photogenerated charge carriers along with the sequence in which these events occur. How-ever, there are no experimental techniques able to determine the sequence (i.e., series, parallel, or combination of both) of these charge transport events and directly determine the QE from charge transport information and vice versa. To address these gaps, here we report a semi-empirical circuit model to determine the sequence of charge transport events and propose a set of hypotheses to discriminate the deciding role of recombination and charge transfer in predicting the QE in a photocatalytic process. By testing with literature data for photocatalytic water splitting, we demonstrate that this model is able to predict QE when the percentage of recom-bination is known and the sequence of charge transport events when QE is known.

Automated summary

Quantum efficiency (QE) is a crucial parameter for evaluating the efficiency of a photocatalyst. However, there is currently no experimental technique that can determine the sequence of charge transport events or directly determine QE from charge transport information. In this study, we propose a semi-empirical circuit model to determine the sequence of charge transport events and suggest hypotheses to differentiate the role of recombination and charge transfer in predicting QE. By testing with literature data, we demonstrate that this model can predict QE when the percentage of recombination is known and determine the sequence of charge transport events when QE is known.