Switching Photocatalytic CO₂ Reduction Path via Controlled Surface Hydroxylation in GO/CoTPP Hybrids

Area of Science:

• Materials Science
• Catalysis
• Environmental Chemistry

Background:

• Photocatalytic CO2 reduction is vital for carbon neutrality and sustainable energy.
• Precise control over product selectivity is a major challenge in CO2 reduction.
• Graphene oxide/cobalt tetraphenylporphyrin (GO/CoTPP) hybrids show promise for CO2 photoreduction.

Purpose of the Study:

• To investigate the role of surface hydroxyl (-OH) density in GO/CoTPP hybrids for selective CO2 reduction.
• To establish a method for tuning -OH concentration on GO supports.
• To elucidate the mechanism of -OH density-dependent pathway control.

Main Methods:

• Gradient reduction of GO supports using hydrazine hydrate to control -OH concentration.
• Systematic characterization of catalyst properties (e.g., oxygen functionalities, hydrophobicity).
• In-situ DRIFTS and KSIE experiments to study reaction mechanisms.

Main Results:

• Tuning GO reduction degree successfully controlled surface -OH density.
• The 8.5% reduced GO/CoTPP catalyst yielded optimal CO production (62.01 μmol g-1 h-1) with 100% selectivity.
• -OH density was identified as a molecular switch regulating reaction pathways (PCET vs. PTET).

Conclusions:

• Surface -OH density critically influences CO2 photoreduction pathways and product selectivity.
• Moderate -OH density optimizes CO selectivity via PCET, while excessive or insufficient -OH leads to by-products or increased energy barriers.
• This study provides design principles for highly selective CO2 photoreduction catalysts based on hydroxylation control.