Photocatalytic Hydrogen Production And Carbon Dioxide Photoreduction By Basic Carbonates And Their Derivative

Photocatalytic water splitting associating with CO₂ reduction is a typical“crown”reaction of artificial photosynthesis process,which can convert solar energy into clean energy.At present,the efficiency of converting solar energy into chemical energy is still relatively low,and this technology is difficult to be applied in industry.The main reason is the serious recombination of photo-generated charge carriers.Therefore,the development of novel photocatalysts is still one of the main efforts in the world,which can not only enhance the light absorption capacity of photocatalysts,but also can greatly reduce the recombination of photo-generated carriers and improve the photocatalytic efficiency.Based on these,the main research contents of this article are as follows:（1）The defect-enriched Zn O/Zn S heterostructures photocatalysts is innovatively prepared by using alkaline zinc carbonate（Zn₅（OH）₆（CO₃）₂）derivatization reaction.Mechanistic analysis shows that interstitial Zn and Zn vacancies exist in the alkaline zinc carbonate derived Zn O.Meanwhile,S vacancies,interstitial S and Zn vacancies are formed in Zn S after sulfurized the alkaline zinc carbonate derived Zn O.Therefore,this defect-enriched Zn O/Zn S photocatalyst displays high response capability to visible light.Under visible light irradiation（λ>400 nm）,the photocatalytic hydrogen production rate on Zn O/Zn S reaches 11.68 mmol g^–1 h^–1,and the optimal hydrogen production rate could reach 27.94 mmol g^–1 h^–1 under simulated sunlight irradiation,which is much higher than most of previously reported Zn O/Zn S-based catalysts.According to energy band structure analysis and selective photo-deposition experiments,it is demonstrated that the photocatalytic reduction sites are mainly located on Zn S and the heterojunction photocatalytic reaction mainly follows typical Z-type photogenerated charge transfer mechanism.This work provides a simple,low-cost,large-scale and practical method for preparing defect-enriched Zn O/Zn S photocatalysts with high photocatalytic activity and stability.（2）Alkaline copper carbonate（Cu₂（OH）₂CO₃）nanorods are prepared by a simple liquid-phase method.UV-Vis DRS and UPS valence band spectroscopy show that Cu₂（OH）₂CO₃ nanorods possesses typical semiconductor characters with a forbidden band width of 3.08 e V.Notably,the valence and conduction band position can satisfy the thermodynamic requirements of CO₂ reduction and H₂O oxidation,respectively.In the absence of sacrificial agent and co-catalyst,Cu₂（OH）₂CO₃ nanorods have excellent stability and selectivity for photocatalytic CO₂ reduction.After five cycles of 25 hours continuous photocatalytic CO₂ reduction reaction,the resulting gas phase products mainly composed of CO（86.7%）,CH₄（4.5%）and H₂（8.8%）.Using isotope experiments combined with in situ differential electrochemical mass spectrometry and in situ infrared spectroscopy,a reasonable explanation is presented for the product source,catalyst evolution,and photocatalytic mechanism of the catalytic system.This study provides an experiment foundation for the development of a highly stable and active alkali carbonate-based photocatalytic system for CO₂ photoreduction.