CuMn_(2)O_(4)/石墨炔S型异质结上锚定氧化助催化剂促进曙红敏化光催化析氢

Anchoring oxidation co‐catalyst over CuMn_(2)O_(4)/graphdiyne S‐scheme heterojunction to promote eosin‐sensitized photocatalytic hydrogen evolution

半导体光催化剂有效的电荷分离及利用是光催化制氢的关键.单一半导体催化剂由于光生电子-空穴对的快速复合导致低的光催化活性,构建异质结是提高光生电荷分离以及电子转移效率的有效方法.此外,助催化剂的引入同样能够促进光催化剂表面电子和空穴的分离,并且其协同效应可促使更多载流子流向相应的助催化剂位点而增强光催化性能.因此,同时构建异质结及合适的氧化位点成为解决光生电子-空穴对有效分离及利用的重要研究方向.本文报道了一种同时构建S型异质结和氧化位点促进CuMn_(2)O_(4)光生电子-空穴对有效分离及利用的可行性策略.虽然在制备CuMn_(2)O_(4)的过程中通过调控制备温度能够自身诱导生成具有氧化能力的Mn_(2)O_(3)来作为氧化位点,但是只存在氧化位点时不能很好地克服光生电子-空穴对的重组现象而导致光催化活性较低.基于此,本文巧妙地利用CuMn_(2)O_(4)自身诱导生成氧化位点的特性并引入石墨炔还原端而构建S型异质结,在氧化位点及S型异质结同时存在的情况下增强光生电子的有效转移.此外,在自身诱导生成氧化位点和S型异质结的协同作用下,促进了复合光催化剂中的光生电子和光生空穴精确定向迁移到相应的还原位点和氧化位点.傅里叶变换红外光谱和拉曼光谱证实成功制备了石墨炔.X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)和高分辨透射电子显微镜(TEM)等结果表明,成功制备了600-CuMn_(2)O_(4)/GDY-40%(6-CG-40%)样品(600°C焙烧,石墨炔质量百分含量为40%).经过组分优化的复合光催化剂6-CG-40%的催化性能达到1586.54μmol g^(‒1)h^(‒1),是CuMn_(2)O_(4)(106.73μmol g^(‒1)h^(‒1))和石墨炔(70.57μmol g^(‒1)h^(‒1))产氢活性的13.86倍和21.48倍高.利用UV-vis光谱、电化学性能和接触角测试等分析6-CG-40%复合光催化剂产氢性能提升的原因,并通过密度泛函理论计算和相关实验表征验证Mn_(2)O_(3)作为氧化助催化剂的合理性.结果表明,原位诱导生成的Mn_(2)O_(3)氧化助催化剂和引入石墨炔构建的S型异质结有效抑制了光生电子-空穴对的复合,从而优化了光生载流子转移效率,最终增强了曙红敏化6-CG-40%光催化析氢性能.综上所述,在控制诱导因子原位生成Mn_(2)O_(4)氧化助催化剂的基础上引入石墨炔还原端构建了S型异质结,在助催化剂与异质结两者的协同作用下极大程度地改善了光生电子-空穴对的严重复合现象,这项工作为解决光催化制氢领域中制约光催化剂制氢能力的关键问题提供了可行性思路.

It is widely acknowledged that efficient charge separation and utilization of photocatalysts are key factors in determing the photocatalytic hydrogen production.Construction of heterojunction has been considered as a promising way to efficiently solve the spatial separation of photogenerated charges.In addition,the introduction of proper cocatalysts can realize the separation of electrons and holes of the photocatalyst and enhance the photocatalytic performance by promoting more carriers to flow to the corresponding active sites.Herein,the S-scheme heterojunction was constructed by introducing graphdiyne into CuMn_(2)O_(4) for photocatalytic hydrogen evolution.Graphdiyne as a reduction semiconductor and in situ produced Mn_(2)O_(3) from CuMn_(2)O_(4) as an oxidation cocatalyst to promote the precisely migration of photogenerated electrons and holes to the corresponding reduction and oxidation sites of photocatalyst.Notably,the photocatalytic performance of the 600-CuMn_(2)O_(4)/GDY-40%(6-CG-40%)could reach 1586.54μmol g^(–1)h^(–1),which is 13.86 and 21.48 times higher than those of CuMn_(2)O_(4)(106.73μmol g^(–1)h^(–1))and graphdiyne(70.57μmol g^(–1)h^(–1)),respectively.Theoretical calculations and experiments results show that both in‐situ induced growth of Mn_(2)O_(3) oxidation co-catalyst and the introduction of graphdiyne to construct S-scheme heterojunction efficiently suppress the severe recombination of photogenerated electron-hole pairs,thus optimizing the photogenerated carrier transfer efficiency,and ultimately leading to the enhanced eosin Y-sensitized photocatalytic hydrogen evolution activity.This work provides a promising method for the construction of oxidation cocatalyst engineered S-scheme heterojunction for solar water splitting.