Surface-Immobilized Rhodium Complex in Vertically Aligned Mesoporous Silica Films for Direct Electroreduction of...

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Direct CO2 reduction (CO2RR) from low-concentration flue gas is challenging due to mass transport limitations and competing hydrogen evolution.
• Heterogenizing molecular catalysts is a promising strategy to enhance CO2RR system scalability and efficiency.

Purpose of the Study:

• To develop and evaluate a formate-selective rhodium complex immobilized on 3D vertically aligned mesoporous silica films (VAMSF) for direct CO2RR.
• To assess the performance of the heterogenized catalyst under both pure and diluted CO2 streams in various media.

Main Methods:

• Electrochemical immobilization of a formate-selective rhodium complex ([Rh(bpy')(Cp*)Cl]Cl) onto VAMSF grown on glassy carbon electrodes.
• Direct CO2RR experiments in organic (acetonitrile/H2O) and aqueous (KHCO3) media under pure and 10% v/v CO2 streams.
• Evaluation of Faradaic efficiency (FE) for formate production and assessment of catalyst stability and recyclability.

Main Results:

• Achieved high formate selectivity with FE up to 66% in pure CO2 and 47% in 10% CO2 (acetonitrile/H2O).
• Demonstrated efficient CO2RR in aqueous media (pH 6.8) with FE of 47% (pure CO2) and 43% (10% CO2).
• Exhibited electrode stability and recyclability without preactivation, indicating no structural degradation.

Conclusions:

• The VAMSF platform effectively supports the heterogenized rhodium complex for direct CO2RR, even under diluted CO2 conditions.
• This work presents the first formate-selective heterogenized molecular complex tested under diluted CO2, paving the way for practical CO2 conversion.
• The developed system shows significant potential for industrial applications in CO2 utilization and emission reduction.