Photoelectrochemical properties of Cu₂O/PANI/Si-based photocathodes for CO₂ conversion

The present study was aimed at converting carbon dioxide (CO₂) into value-added products such as methanol, which can provide not only a potential solution for controlling the carbon dioxide concentration level in the atmosphere but also can offer an alternative approach for the production of renewable energy sources. From this perspective, various hybrid photoelectrocatalysts were synthesized, characterized and used as photocathodes for photoelectrochemical (PEC) reduction of carbon dioxide to methanol in an aqueous medium under visible light irradiation. Flat silicon (Si) and pyramidal textured silicon (SiPY) substrates, covered with polyaniline (PANI) with or without sensitization with copper (I) oxide (Cu₂O) particles, were investigated. It was observed that the combination of PANI and copper (I) oxide greatly increased PEC carbon dioxide reduction to methanol owing to the enhancement in the carbon dioxide chemisorption capacity by the photocathode surface and at the same time facilitated the separation of photogenerated electron–hole (e⁻/h⁺) pairs. The PEC results demonstrated that the applied potential impacts the photocurrent stability. Sensitization with copper (I) oxide effectively separated the photogenerated e⁻/h⁺ pairs and, therefore, enhanced the PEC carbon dioxide reduction activity of the hybrid photocatalyst. The best faradaic efficiency for methanol formation reached 57.66%, which was recorded when the copper (I) oxide/PANI/SiPY heterostructure was used as a photocathode at an applied potential of −1.2 V against the saturated calomel electrode.