The Application Of Cu₂?OH?₂CO₃ As Cocatalyst For H₂ Evolution From Photocatalytic Water Splitting

Energy is the material basis for sustainable development and economic prosperity,and the environment is connected with people's daily life and health.Since twenty-first Century,the global economic recovered and developed rapidly.However,these were based on the huge consumption of fossil fuels,and the environmental problems became increasingly prominent.The two worldwide problems of energy consumption and environment pollution attracted the attentions of scholars from all over the world,it's urgent to solve.Semiconductor photocatalytic technology can use solar energy to decompose water to produce hydrogen,or to reduce carbon dioxide into hydrocarbon fuels,etc.,it can solve these problems effectively.Since 1972,Japanese scientists Fujishima and Honda reported that TiO₂ electrode can be used for photocatalytic water splitting.Semiconductor photocatalytic water splitting into hydrogen was generally considered as a potential way,which can transform inexhaustible solar energy into clean chemical energy.Herein,highly efficient and stable Cu₂?OH?₂CO₃/TiO₂ photocatalysts for hydrogen generation are prepared by incorporating Cu₂?OH?₂CO₃ clusters onto the surface of TiO₂ through a facile precipitation method.The obtained Cu₂?OH?₂CO₃/TiO₂ photocatalyst with optimal Cu₂?OH?₂CO₃ content of 0.5 mol%shows an outstanding photocatalytic H₂-production rate of 6713?mol h^?1 g^?1?with apparent quantum efficiency of 15.4%at 365 nm?,which is comparable to the excellent Pt/TiO₂ photocatalyst and more efficient than other copper specie modified TiO₂ photocatalyst.The formation of Cu₂?OH?₂CO₃/Cu⁺/Cu⁰ clusters essentially contribute to the enhanced H₂-production activity by reducing the over-potential of water reduction and promoting the transfer of photogenerated electrons from the conduction band of TiO₂ to the Cu₂?OH?₂CO₃/Cu⁺/Cu⁰ clusters.A high stability of the Cu₂?OH?₂CO₃/TiO₂ photocatalyst is achieved due to the re-oxidation process of Cu⁺/Cu⁰ to Cu₂?OH?₂CO₃ and structure confinement of Cu₂?OH?₂CO₃ clusters in the mesopores of TiO₂.This work brings in new insight in developing low-cost noble-metal-free photocatalytic system for solar-to-fuel conversion.Moreover,We prepared g-C₃N₄/rGO/Cu₂?OH?₂CO₃ ternary composite used for photocatalytic water splitting for hydrogen production.The porous g-C₃N₄nanosheet was obtained by calcination twice,and then the graphene oxide?GO?was reduced to g-C₃N₄ in situ by chemical oxidation method.g-C₃N₄ and rGO can be closely combined.Finally,the Cu₂?OH?₂CO₃ was loaded through facile precipitation method.The results showed that samples of pure g-C₃N₄ and g-C₃N₄/rGO composite exhibited little hydrogen production activity.This is because the rapid recombination of photo-generated carriers,the photo-produced electrons cannot be efficiently used for the reduction of hydrogen ions into hydrogen.Although the g-C₃N₄ composited with rGO can inhibit the recombination of photogenerated electron and hole pairs to a certain extent,the photocatalytic water splitting reaction was restricted by the large kinetic barrier without the cocatalyst.The composite samples of g-C₃N₄ and Cu₂?OH?₂CO₃ showed high photocatalytic activity for hydrogen production.And after loading certain amount of Cu₂?OH?₂CO₃,it can serve as cocatalyst to promote the transfer of photo-generated electrons effectively,can also reduce the overpotential for water splitting,accelerate the photocatalytic reaction.Compared with the binary composite g-C₃N₄/Cu₂?OH?₂CO₃,the photocatalytic water splitting activity of the g-C₃N₄/rGO/Cu₂?OH?₂CO₃ ternary composite increased significantly,this can be ascribed to the existence of the rGO,which can further accelerate the transfer of photo-generated electrons.