About Control: Kinetics in Molecule- based Photochemical Water Reduction Investigated by Transient IR Spectroscopy.

Kerstin T Oppelt,Peter Hamm

doi:10.2533/chimia.2021.188

Abstract

This review aims to promote the role of transient IR spectroscopy to investigate molecular-based photocatalytic water reduction. Examples are discussed in which this method has been successfully applied to elucidate reaction mechanisms. Focus is given to kinetic changes and their consequences when a photochemical water reduction system, which is functional and well understood in solution, is brought onto a metal oxide surface.

Highlights

The field of artificial photosynthesis and photochemical water splitting has grown to a substantial size in the last 20 years, as part of an even larger field of research dedicated to renewable fuels, solar energy harvest and storage
This review aims to promote the role of transient IR spectroscopy to investigate molecular-based photocatalytic water reduction
A large number of review articles on artificial photosynthesis can be found in the literature

Summary

Introduction

The field of artificial photosynthesis and photochemical water splitting has grown to a substantial size in the last 20 years, as part of an even larger field of research dedicated to renewable fuels, solar energy harvest and storage. We will discuss the potential of time-resolved infrared spectroscopy to investigate reaction mechanisms of molecule-based water reduction systems. We can compare the decay of the excited state vibrations of the Re complex with or without quencher, observe reductive quenching by the appearance of a new set of frequency-shifted bands and infer charge transfer to the cobalt WRC from their subsequent decay. An example for a semi-heterogeneous model system is shown, right,[49] with ZrO2 as redox-inactive substrate It is our primary example, where the same reaction steps are expected to occur as in a solution-phase system with very similar molecular components. Scheme of the basic processes in a solution-phase system with the various molecular components shown on the left, and the corresponding surfacebased system on the right

CoII CoI

Normalized D Abs

Findings

Normalized Amplitude