Photo-Activating Biomimetic Polyoxomolybdate for Boosting Oxygen Evolution in Neutral Electrolytes

Area of Science:

• Inorganic Chemistry
• Photochemistry
• Electrochemistry

Background:

• The oxygen evolving center (OEC) in photosystem II (PS-II) utilizes metal-oxo clusters for efficient charge separation and catalysis.
• Developing artificial catalysts that mimic PS-II's OEC for the oxygen evolution reaction (OER) in neutral electrolytes is a significant challenge.

Purpose of the Study:

• To design and synthesize a novel photochromic polyoxomolybdate catalyst inspired by the OEC of PS-II.
• To investigate its performance as a biomimetic OER catalyst in neutral electrolytes.
• To explore the mechanism of enhanced OER activity following photoinduced electron transfer (PIET).

Main Methods:

• Synthesis of a crystalline photochromic polyoxomolybdate, MV2[β-Mo8O26] (1).
• Photoirradiation to induce color change and PIET.
• Electrochemical characterization to evaluate OER performance (overpotential, Tafel slope).
• Experimental and theoretical studies to elucidate the catalytic mechanism.

Main Results:

• The synthesized material exhibits photochromism, changing from colorless to gray upon PIET.
• The colored state remains ultra-stable in a charge-separated state for over a year.
• Significant decrease in overpotential and Tafel slope observed for the colored state.
• The colored catalyst demonstrates superior OER performance in neutral electrolytes compared to RuO2.
• Oxygen holes within polyanions after irradiation were identified as active sites for O-O coupling.

Conclusions:

• A novel photochromic polyoxomolybdate catalyst mimicking PS-II's OEC has been successfully developed.
• Photoinduced electron transfer leads to enhanced OER activity through the formation of active oxygen hole sites.
• This work represents the first application of electron-transfer photochromism to boost OER catalytic activity.