Hydrophobic surface efficiently boosting Cu₂O nanowires photoelectrochemical CO₂ reduction activity

The limited mass transfer of CO₂ and the competitive hydrogen evolution reaction (HER) during photoelectrochemical (PEC) CO₂ reduction usually result in low CO₂ reduction activity. Here, we constructed a Cu₂O/Sn/PTFE photocathode with a hydrophobic surface based on Cu₂O by physical vapor deposition and a dipping method. The CO faradaic efficiency (FE) increased from 34.5% (Cu₂O) to 95.1% (Cu₂O/Sn/PTFE) at -0.7 V vs. RHE, and the FE_H2 decreased from 27.9% (Cu₂O) to 3.8% (Cu₂O/Sn/PTFE). The introduction of the hydrophobic layer enhances the local CO₂ concentration on the electrode surface and effectively isolates H⁺ from the aqueous electrolyte, thereby enhancing the CO₂ reduction activity.