Molecular–Polymeric Hybrid Photocathodes for CO₂ Reduction: A Modular Approach to Sustainable Photoelectrocatalysis

Abstract

The development of efficient and sustainable photocathodes is central to advancing photoelectrocatalytic CO₂ reduction. Here, we report CP/PPy/Re–Ru, a hybrid molecular–polymeric photocathode prepared in a simple two-step process by depositing catalytically active Re–Ru complexes onto a polypyrrole backbone on carbon paper. The approach is resource-efficient and modular. Under photoelectrocatalytic conditions at −1.4 V versus normal hydrogen electrode (NHE), the material achieved ∼15 µmol CO formation within 1 h at Faradaic efficiencies of 60%–70%. Continuous CO evolution was maintained for up to 7 h even in membrane-free operation, yielding ∼90 µmol CO while avoiding the use of polyfluoroalkyl substance (PFAS)-based membranes. Reusability was further demonstrated across multiple cycles, confirming the robustness of the concept. Postreaction analyses indicated structural changes, pointing to opportunities for future optimization of long-term stability. Overall, CP/PPy/Re–Ru provides a versatile and sustainable platform that combines straightforward preparation with promising activity and adaptability, offering a valuable foundation for next-generation CO₂ reduction technologies.