Time-Resolved Spectroelectrochemical Observation of Overlayer-Induced Charge Carrier Dynamics in Water Photooxidation

Area of Science:

• Materials Science
• Electrochemistry
• Surface Chemistry

Background:

• Efficient solar fuel production relies on optimized photoelectrodes.
• Understanding the semiconductor-electrolyte interface (SEI) is critical for improving photoelectrochemical (PEC) devices.
• Current methods lack detailed insights into interfacial reaction mechanisms.

Purpose of the Study:

• To elucidate the key factors governing interfacial reactions in PEC systems.
• To investigate the role of amorphous TiO2 overlayers on WO3 photoanodes.
• To provide strategies for designing advanced surface-modified PEC devices.

Main Methods:

• Operando spectroelectrochemistry was employed to study a model WO3/TiO2 photoelectrode system.
• Transient absorption spectroscopy was used to probe ultrafast interfacial phenomena.
• Surface and bulk properties of the photoanode were analyzed.

Main Results:

• Amorphous TiO2 overlayers enhanced n-type semiconductor characteristics of WO3.
• TiO2 overlayers healed oxygen vacancies, reducing charge carrier recombination.
• A 1.5-fold increase in Faradaic efficiency was observed.
• Operando spectroscopy revealed accelerated electron transfer and increased hole population due to band bending.

Conclusions:

• Band bending in the space-charge region is a key factor in interfacial reactions for PEC devices.
• Surface modification with TiO2 overlayers is a viable strategy for enhancing PEC performance.
• The study provides a mechanistic understanding linking ultrafast processes to water oxidation kinetics.