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

Reducing CO 2 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 (Cu 2 O), a low-cost semiconductor, is one of the promising candidates for application in CO 2 RR systems. However, the performance is still unsatisfactory, and the products, like acids and alcohols, can be obtained regarding the system parameters. Cu 2 O's main drawback is its susceptibility to photo corrosion, which limits its effectiveness in the CO 2 reduction reaction (CO 2 RR) due to instability. The presence of Cu + on the electrode surface is essential for suppressing hydrogen evolution and improving CO 2 RR selectivity. In this study, we explore the use of polyethyleneimine (PEI) to enhance the performance of Cu 2 O electrodes and protect against photo corrosion. We hypothesized that PEI's amine groups would bind CO 2 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 Cu 2 O. Under illumination at 0.3 V vs. RHE, the PEI@Cu 2 O photocathode produces methanol, ethanol, and formate species. Our preliminary findings suggest that PEI might be an effective tool for CO 2 capture and utilization. • A new approach is proposed to improve the structure of 3D Cu₂O photocathodes. • Cost-effective, abundant, non-toxic polyelectrolyte were introduced as modifiers and stabilizers for the CO₂RR process. • PEI/ALG exhibit enhanced durability compared to PEI-only coatings, likely due to reduced diffusion from the electrode surface. • A stable CO₂ reduction process was maintained continuously for 20 h.