Translating Catalyst-Polymer Composites from Liquid to Gas-Fed CO₂ Electrolysis: A CoPc-P4VP Case Study

The electrochemical CO₂ reduction reaction (CO₂RR) in gas-fed flow electrolyzers using gas diffusion electrodes (GDEs) generates industrially relevant activities and provides a promising approach for carbon recycling. Developing effective catalyst systems on GDEs is critical for achieving high activities. Catalyst-polymer composites (CPCs) formed between immobilized molecular catalysts and coordinating polymers exhibit positive synergies for the enhancement of CO₂RR activity. However, previous studies of CPCs have been primarily confined to liquid reaction platforms, and there are few examples of translating CPCs to GDE architectures. This suggests a knowledge gap exists in translating between the two platforms. Herein, we identify and bridge that gap by demonstrating a case study for the (poly-4-vinylpyridine)-encapsulated cobalt phthalocyanine (CoPc-P4VP) CPC. We identify a major knolwedge gap in the overlooked factor of CPC's hydrophobicity, which plays a significant role in gas-fed CO₂RR but is often neglected in fundamental studies conducted on the liquid reaction platform. We bridge this gap by correlating catalyst hydrophobicity in liquid CO₂RR with activity in gas-fed CO₂RR by means of water contact angle measurements. Our case study underscores the importance of incorporating an engineering perspective into CPC studies and the necessity to consider hydrophobicity in CPC design and evaluation. This approach will hopefully accelerate the applied studies of this group of promising catalytic materials in gas-fed CO₂ electrolysis.