双功能S-型g-C3N4/Bi/BiVO4复合光催化剂驱动人工碳循环（英文）

长期以来,陆地、大气和海洋之间的碳循环维持了大自然碳平衡.随着密集人类活动和高度工业发展,碳燃料、碳化学品和碳材料广泛应用于各个领域,导致碳排放过量,碳平衡已被严重破坏,碳污染已成为一个严峻问题.例如,持久性有机污染物和挥发性有机化合物过量排放到环境中,威胁着人类的健康和生态平衡.人们陆续开发出各种先进的环境技术,如微生物分解,去除空气和水中的碳基污染物,将有毒有害的有机化合物转化为无害CO2.但是,CO2本身是大气中的主要温室气体,它在大气中的浓度早超过了天然碳循环所能维持的环境自洁净能力.基于先进催化技术建立人工碳循环,将有机污染物矿化生成的CO2进一步转化为有价值的有机化学品(如太阳能燃料)是一种理想的低碳方法.光合作用是自然碳循环中核心过程之一,是降低大气中CO2浓度的关键.受到光合作用启发,科学家们积极开发人工光合成技术推动CO2资源化.人工光合成技术本质上基于半导体光催化过程.半导体光催化过程具有双重作用.一方面,基于有氧光催化氧化过程,有机污染物可以矿化生成无毒CO2.另一方面,基于缺氧光催化还原过程,CO2可以转化为碳氢化合物太阳能燃料.理论上,结合上述两个过程,为建立人工碳循环奠定基础,但是,至今很少有人成功建立有氧氧化-无氧还原串联光催化工艺,实现人工碳循环.难点在于有机污染物的有氧氧化反应和CO2的无氧还原反应的操作条件与反应机制是完全不同的,目前缺乏同时适用于上述两种反应的双功能光催化剂.本文成功构建了具有双功能的g-C3N4/Bi/BiVO4三元复合光催化剂,它不仅在降解有机污染物方面表现出优异的有氧光催化氧化性能(以降解染料罗丹明B为例),而且还表现出优异的缺氧CO2光催化还原性能.此外,基于“一锅法”厌氧耦合氧化-还原反应,g-C3N4/Bi/BiVO4三元复合光催化剂成功实现同步罗丹明B降解与太阳能燃料生成,构建了从毒害有机污染物到高品质太阳燃料的碳循环.结合牺牲剂实验分析与密度泛函理论理论计算,作者提出g-C3N4/Bi/BiVO4复合光催化剂的双功能性与g-C3N4与BiVO4界面内建S-型复合异质结有关.S-型复合异质结既促进界面电荷转移与分离,又维持了最佳电荷氧化还原电位.此外,S型g-C3N4/Bi/BiVO4复合光催化剂中原位生成的具有等离子体效应的Bi纳米颗粒具有双重作用,既促进界面电荷定向转移,又促进可见光吸收.本文开发的新型双功能S-型g-C3N4/Bi/BiVO4复合光催化剂系统为进一步开发集成式有氧-缺氧光催化碳循环反应系统奠定基础.

Bifunctional S-scheme g-C3N4/Bi/BiVO4 hybrid photocatalysts toward artificial carbon cycling

Although both the aerobic photocatalytic oxidation of organic pollutants into CO2 and the anaerobic photocatalytic reduction of CO2 into solar fuels have been intensively studied,few efforts have been devoted to combining these carbon-involved photocatalytic oxidation-reduction processes together,by which an artificial photocatalytic carbon cycling process can be established.The key challenge lies in the exploitation of efficient bifunctional photocatalysts,capable of triggering both aerobic oxidation and anaerobic reduction reactions.In this work,a bifunctional ternary g-C3N4/Bi/BiVO4 hybrid photocatalyst is successfully constructed,which not only demonstrates superior aerobic photocatalytic oxidation performance in degrading an organic pollutant(using the dye,Rhodamine B as a model),but also exhibits impressive photocatalytic CO2 reduction performance under anaerobic conditions.Moreover,a direct conversion of Rhodamine B to solar fuels in a one-pot anaerobic reactor can be achieved with the as-prepared ternary g-C3N4/Bi/BiVO4 hybrid photocatalyst.The excellent bifunctional photocatalytic performance of the g-C3N4/Bi/BiVO4 photocatalyst is associated with the formation of efficient S-scheme hybrid junctions,which contribute to promoting the appropriate charge dynamics,and sustaining favorable charge potentials.The formation of the S-scheme heterojunction is supported by scavenger studies and density functional theory calculations.Moreover,the in-situ formed plasmonic metallic Bi nanoparticles in the S-scheme hybrid g-C3N4/Bi/BiVO4 photocatalyst enhances vectorial interfacial electron transfer.This novel bifunctional S-scheme g-C3N4/Bi/BiVO4 hybrid photocatalyst system provides new insights for the further development of an integrated aerobic-anaerobic reaction system for photocatalytic carbon cycling.