Aiming a selective reduction of CO₂ to methanol, a p-n junction semiconductor was constructed based on CuO nanospheres (NsCuO) deposited at TiO₂ nanotubes (NtTiO₂). The NtTiO₂/NsCuO material demonstrated smaller charge transfer resistance, smaller flat band potential and wider optical absorption when compared with NtTiO₂ and/or Ti/TiO₂ nanoparticles coated by higher size particles of CuO (Ti/TiO₂/CuO). The selective reduction of dissolved CO₂ to methanol was promoted at lower potential of +0.2 V and UV–vis irradiation in 0.1 mol L⁻¹ K₂SO₄ electrolyte pH 8 with 57% of faradaic efficiency. Even though the performance of the nanostructured material NtTiO₂/NsCuO was similar to the non-completely nanostructured material Ti/TiO₂/CuO (0.1 mmol L⁻¹ methanol), the conversion to methanol has been significantly increased when hydroxyls (0.62 mmol L⁻¹) and holes scavengers (0.71 mmol L⁻¹), such as p-nitrosodimethylaniline (RNO) or glucose, respectively, were added in the supporting electrolyte. It indicates that photogenerated electron/hole pairs are spatially separated on p-n junction electrodes, which produces effective electrons and long-life holes, influencing the products formed in the reaction. A schematic representation of the heterojunction effect on the photoelectrocatalytic CO₂ reduction is proposed under the semiconductor and each supporting electrolyte, which improves the knowledge about the subject.

为了选择性地将CO ₂还原为甲醇，基于沉积在TiO ₂纳米管（NtTiO ₂）上的CuO纳米球（NsCuO）构建了pn结半导体。与由较大尺寸的CuO颗粒（Ti / TiO ₂ / CuO）包覆的NtTiO ₂和/或Ti / TiO ₂纳米颗粒相比，NtTiO ₂ / NsCuO材料具有更小的电荷转移阻力，更小的平带电势和更宽的光吸收。在较低的+0.2 V电位和0.1 mol L ^-1 K ₂ SO _4中的UV-vis照射下，促进了溶解的CO ₂选择性还原为甲醇。pH为8的电解质，具有法拉第效率的57％。即使纳米结构材料NtTiO ₂ / NsCuO的性能类似于非完全纳米结构材料Ti / TiO ₂ / CuO（0.1 mmol L ^-1甲醇），当羟基（0.62 mmol L ^-1）和空穴清除剂（0.71 mmol L ^-1）（例如对亚硝基二甲基苯胺（RNO）或葡萄糖）分别添加到支持电解质中。这表明光生电子/空穴对在pn结电极上在空间上分开，从而产生有效的电子和长寿命的空穴，从而影响反应中形成的产物。在半导体和每种支持电解质下，提出了异质结对光电催化CO ₂还原的影响的示意图，从而提高了有关该主题的知识。