Enhancing photoelectrochemical CO2 reduction: The impact of polyelectrolytes modification on copper oxide catalysts

Abstract

Reducing CO₂ into value-added chemicals and fuels by artificial photosynthesis is a critical turnover in research as one of the considerable solutions to global environmental and energy issues. Copper (I) oxide (Cu₂O), a low-cost semiconductor, is one of the promising candidates for application in CO₂RR systems. However, the performance is still unsatisfactory, and the products, like acids and alcohols, can be obtained regarding the system parameters. Cu₂O's main drawback is its susceptibility to photo corrosion, which limits its effectiveness in the CO₂ reduction reaction (CO₂RR) due to instability. The presence of Cu⁺ on the electrode surface is essential for suppressing hydrogen evolution and improving CO₂RR selectivity. In this study, we explore the use of polyethyleneimine (PEI) to enhance the performance of Cu₂O electrodes and protect against photo corrosion. We hypothesized that PEI's amine groups would bind CO₂ and facilitate its transformation into intermediate products during reduction reactions. Chronoamperometry and mass spectrometry results showed that, after 20 h, the photostability of PEI-coated electrodes was significantly improved compared to bare Cu₂O. Under illumination at 0.3 V vs. RHE, the PEI@Cu₂O photocathode produces methanol, ethanol, and formate species. Our preliminary findings suggest that PEI might be an effective tool for CO₂ capture and utilization.