碳铂双助催化剂增强CdS空心球光催化产氢性能

Enhanced photocatalytic H_(2) production performance of CdS hollow spheres using C and Pt as bi-cocatalysts

利用半导体光催化分解水产氢是将太阳能转换为化学能最有前景的方法之一.在众多的半导体光催化剂中,硫化镉(CdS)不仅具有可见光响应的带隙值(约2.4 eV),而且其导带底和价带顶的能级横跨于水的氧化还原电势两端,能够在可见光照射下分解水产氢,这使得CdS成为一种热门的光催化剂而被广泛研究.然而,单一CdS由于光生电子−空穴对复合速率快、光腐蚀严重等缺点,其光催化产氢活性并不高.为了克服这些缺点,人们探索了多种改性策略,如形貌和结构调控、构建异质结以及负载助催化剂等.负载助催化剂由于可以增强光吸收、促进光生电荷分离以及提供更多活性位点,被认为是一种有效的改性策略.然而,目前大部分的助催化剂都是金属材料,不仅价格昂贵,而且容易对环境造成污染破坏.碳材料因为具有经济环保、导电性能优异、化学稳定性好、光吸收能力和光热效应强等优点,成为一种有望实现太阳能高效综合利用的非金属助催化剂.其中,空心碳球还具有质量轻、比表面积大以及光利用率高等独特优势,吸引了广大科研工作者的注意.本文选取多孔碳空心纳米球(C-HS)作为模板,通过简单的水热法制备了carbon@CdS空心球(C@CdS-HS)复合光催化剂,并将其用于光催化分解水产氢.作为对照,在相同的条件下制备了单一的CdS空心球(CdS-HS).在模拟太阳光照射下并沉积1.0 wt%Pt后,C@CdS-HS/Pt的光催化产氢速率高达20.9 mmol h^(−1)g^(−1)(420 nm处的表观量子效率为15.3%),分别是CdS-HS、C@CdS-HS和CdS-HS/Pt的69.7、13.9和3.9倍.通过一系列表征手段,揭示了光生电荷的传输路径,并提出了C@CdS-HS/Pt光催化活性增强的机理,多孔C-HS的引入提高了复合光催化剂的比表面积,增加了反应活性位点;导电性良好的C-HS可以起到贮存和传导光生电子的作用,从而提高光生载流子的分离和传输效率;CdS纳米颗粒原位生长在C-HS表面形成紧密接触的界面,有利于光生电荷在界面间的传输;C-HS吸收红外光产生很强的光热效应,可以使复合光催化剂的表面温度显著升高,在动力学上提高催化剂的产氢速率;C-HS和Pt作为双助催化剂具有明显的协同效应,可以显著提高CdS的光催化产氢活性.

Photocatalytic H2 production from water splitting is an effective method to solve energy crisis and environmental pollution simultaneously.Herein,carbon@CdS composite hollow spheres(C@CdS-HS)are fabricated via a facile hydrothermal method using porous carbon hollow spheres(C-HS)as the template.The C@CdS-HS shows an excellent photocatalytic H2-generation rate of 20.9 mmol h^(−1) g^(−1)(apparent quantum efficiency of 15.3%at 420 nm),with 1.0 wt%Pt as a cocatalyst under simulated sunlight irradiation;this rate is 69.7,13.9,and 3.9 times higher than that obtained with pure CdS hollow spheres(CdS-HS),C@CdS-HS,and CdS-HS/Pt,respectively.The enhanced photocatalytic H_(2)-evolution activity of C@CdS-HS/Pt is due to the synergistic effect of C and Pt as the bi-cocatalyst.The C-HS serves not only as an active site provider but also as an electron transporter and reservoir.Moreover,C-HS has a strong photothermal effect that is induced by near infrared light,which kinetically accelerates the H_(2)-production reaction.Additionally,the underlying charge transfer pathway and process from CdS to C−HS is revealed.This work highlights the potential application of C-HS-based nanocomposites in solar-to-chemical energy conversion.