The Performance And Deactivation Mechanism Of Cu₂O In Photocatalytic Water Splitting

Conversion of solar energy into hydrogen energy has potential application in solving the current energy and environmental issues.Cuprous oxide is a kind of potential p-type photoelectric catalyst material because of its easy preparation,low cost and high photoelectric conversion efficiency.In this work,we prepared Cu₂O thin films with exposing different crystal facets.The results of SEM and XRD indicate that Cu₂O crystal tend to grow along{100}direction and expose much more{111}crystal facets in acidic conditions.In alkaline solutions Cu₂O crystal tend to expose much more{100}crystal facets.The photocatalytic performance of the Cu₂O thin films is tested with a three-electrode system.According to the U-I curves,we found that Cu₂O thin film show higher activity with the increase of{100}crystal facets,indicating that{100}crystal facets are the active face compared to the{111}crystal facets.According to the T-I curves,much more{111}crystal facets mean slower deactivation rate,which means that the{111}crystal facets are the stable face compared to the{100}crystal facets.To reveal the deactivation mechanism of Cu₂O.We used hydro-thermal synthesis method to prepare Cu₂O crystallites selectively exposing to different crystal facets.Manganese ion(Mn²⁺)was used as a tracker of the photo-generated holes and Sn²⁺was used as a tracker of the photo-generated electrons.The results indicate that photo-generated holes tend to gather on the{100}crystal facets while the photo-generated electrons transfer to every crystal facets,which leads to the easy deactivation of{100}crystal facets.Copper?I?oxide is firstly oxidized to Cu²⁺,then Cu²⁺is reduced by the photo-generated electrons and deposits as Cu?0?on the surface.