碱式铜盐包覆Cu2O催化剂的形成机理及催化性能

The Formation Mechanism and Catalytic Performance of Cu2O Coated Basic Copper Salt Core-Shell Catalyst

采用硫酸铜与4种碱NaOH、Na2CO3、Na2SO3、Na2S2O3在室温(25℃)下反应,并在Cu2O表面包覆碱式铜盐,均得到组成为Cu2O@Cu4(SO4)(OH)6的核壳型催化剂,其中,由Na2S2O3制备的样品其催化活性远高于其他碱制备的样品.通过性质表征可知,由Na2S2O3制得样品具有核内部孔洞多、缺陷分布广、活性表面大、表面粗糙、晶体紧实度低等特点,这些特征均有利于催化活性的提高.进一步研究确认,Na2S2O3在反应中具有多种作用,一是水解提供OH^-;二是自身发生歧化反应或者与Cu^2+发生氧化还原反应生成SO^2-4和S^2-,提供形成Cu4(SO4)(OH)6所需的SO^2-4;三是能与Cu2O核反应,使其溶解形成孔洞.因此,采用铜盐与Na2S2O3在室温下反应形成的核壳型催化剂Cu2O@Cu4(SO4)(OH)6具有非常高的催化活性,在黑暗条件下能高效降解高浓度(400mg/L)的染料(橙黄II),反应2h后降解率可达99.5%.

The core-shell catalysts which have the same composition of Cu 2O@Cu 4(SO 4)(OH) 6 were synthesized through the reaction at room temperature (25 ℃) of copper sulphate with four kinds of alkalies,including NaOH,Na 2CO 3,Na 2SO 3 and Na 2S 2O 3. Of them,the sample prepared with Na 2S 2O 3 exhibits the highest catalytic activity. The characterization results show that the sample prepared by Na 2S 2O 3 possesses many holes and defects in the interior of the core,large surface area,rough surface and low crystal compactness,which are beneficial to the enhancement of catalytic activity. There are several roles of Na 2S 2O 3 in the reaction. Firstly,Na 2S 2O 3 hydrolyzes to provide OH ^- group. Then it disproportionates or reacts with Cu^ 2+ ion through redox to generate SO^ 2- 4 and S ^2- ions,which provides SO ^2- 4 for forming Cu 4(SO 4)(OH) 6 crystal. Besides,Na 2S 2O 3 can react with Cu 2O core,resulting in the generation of holes in the interior of Cu 2O. Hence the core-shell catalyst Cu 2O@Cu 4(SO 4)(OH) 6 synthesized with Na 2S 2O 3 shows very high catalytic activity. The catalyst can almost completely degrade dye (AO7) with high concentration (400 mg/L) in 2 h under dark condition.