Enhanced photocatalytic H₂ production performance of CdS hollow spheres using C and Pt as bi-cocatalysts

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 H₂-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 H₂-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.
利用半導體光催化分解水產氫是將太陽能轉換為化學能最有前景的方法之一。在眾多的半導體光催化劑中，硫化鎘（CdS）不僅具有可見光響應的帶隙值（約2.4 eV），而且其導帶底和價帶頂的能級橫跨於水的氧化還原電勢兩端，能夠在可見光照射下分解水產氫，這使得CdS成為一種熱門的光催化劑而被廣泛研究。然而，單一CdS由於光生電子—空穴對復合速率快、光腐蝕嚴重等缺點，其光催化產氫活性並不高。為了克服這些缺點，人們探索了多種改性策略，如形貌和結構調控、構建異質結以及負載助催化劑等。負載助催化劑由於可以增強光吸收、促進光生電荷分離以及提供更多活性位點，被認為是一種有效的改性策略。然而，目前大部分的助催化劑都是金屬材料，不僅價格昂貴，而且容易對環境造成污染破壞。碳材料因為具有經濟環保、導電性能優異、化學穩定性好、光吸收能力和光熱效應強等優點，成為一種有望實現太陽能高效綜合利用的非金屬助催化劑。其中，空心碳球還具有質量輕、比表面積大以及光利用率高等獨特優勢，吸引了廣大科研工作者的注意。本文選取多孔碳空心納米球（C-HS）作為範本，通過簡單的水熱法制備了carbon@CdS空心球（C@CdS-HS）復合光催化劑，並將其用於光催化分解水產氫。作為對照，在相同的條件下制備了單一的CdS空心球（CdS-HS）。在模擬太陽光照射下並沉積1.0 wt%Pt後，C@CdS-HS/Pt的光催化產氫速率高達20.9 mmol h⁻¹ g⁻¹（420 nm處的表觀量子效率為15.3%），分別是CdS-HS、C@CdS-HS和CdS-HS/Pt的69.7、13.9和3.9倍。通過一系列表徵手段，揭示了光生電荷的傳輸路徑，並提出了C@CdS-HS/Pt光催化活性增強的機理，多孔C-HS的引入提高了復合光催化劑的比表面積，增加了反應活性位點；導電性良好的C-HS可以起到貯存和傳導光生電子的作用，從而提高光生載流子的分離和傳輸效率；CdS納米顆粒原位生長在C-HS表面形成緊密接觸的介面，有利於光生電荷在介面間的傳輸；C-HS吸收紅外光產生很強的光熱效應，可以使復合光催化劑的表面溫度顯著升高，在動力學上提高催化劑的產氫速率；C-HS和Pt作為雙助催化劑具有明顯的協同效應，可以顯著提高CdS的光催化產氫活性。 Copyright © 2021 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences.