Optimized Multi‐Step Anodization of Cu₂O/TiO₂ Nanotube Arrays for CO₂ Reduction

Abstract Highly ordered Cu 2 O/TiO 2 nanotube arrays (Cu 2 O/TNTAs) composite electrodes were fabricated using a novel multi‐step anodization process and gradient‐based feedback gain ( K p ) optimization. Uniform Cu 2 O coverage on TNTAs was achieved via precise voltage‐controlled electrodeposition. The optimized 60 s‐Cu₂O/TNTAs electrode demonstrated a high photocurrent density of 0.60 mA cm −2 and maintained stability over 8 hours under photoelectrochemical CO₂ reduction conditions. Electrochemical analyses reveal that moderate Cu 2 O deposition enhances electron transfer and increases the active surface area, while excessive deposition reduces performance. These results demonstrate a scalable, cost‐effective strategy for developing efficient photoelectrocatalysts for solar‐driven CO₂ conversion.