Division of Nanomaterials and Chemistry, Hefei National Laboratory for Physical Sciences at Microscale Department, University of Science and Technology of China, Hefei 230026, P. R. China.
Nanoscale. 2015 Mar 19;7(13):5752-9. doi: 10.1039/c4nr06949h.
As semiconductor-based nanoheterostructures play a decisive role in current electronics and optoelectronics, the introduction of active heterojunctions can afford new and improved capabilities that will enhance the conversion of solar energy into chemical energy. In this work, a novel metal/semiconductor MoO₂/Zn₀.₅Cd₀.₅S heterojunction has been designed and prepared to significantly enhance photocatalytic H₂ production efficiency. The photocatalytic activity of the as-prepared MoO₂/Zn₀.₅Cd₀.₅S for H₂ generation from water under visible-light irradiation (λ ≥ 420 nm) is measured. MoO₂/Zn₀.₅Cd₀.₅S hybrid nanoparticles have a higher photocatalytic activity than Zn₀.₅Cd₀.₅S even without the noble metal cocatalyst. The results show that the rate of H₂ evolution over annealed MoO₂/Zn₀.₅Cd₀.₅S is about 13 times higher than that of Zn₀.₅Cd₀.₅S alone, and 10 times higher than that of simply mixed MoO₂/Zn₀.₅Cd₀.₅S. Implying that the strong coupling at the interface of MoO₂ and Zn₀.₅Cd₀.₅S facilitates electron transfer from the conduction band of Zn₀.₅Cd₀.₅S to metallic MoO₂, thus promoting the separation of photogenerated electrons and holes. MoO₂ (2 wt%)/Zn₀.₅Cd₀.₅S heterostructured photocatalyst calcined at 673 K achieves the optimal overall activity for H₂ evolution. The introduction of metallic MoO₂ cocatalyst leads to a remarkable improvement in the photo current and photocatalytic H₂ production activity of Zn₀.₅Cd₀.₅S, and the content of MoO₂ in this catalyst has an important influence on the photocatalytic activity. It is shown that 2 wt% metallic MoO₂ loaded on Zn₀.₅Cd₀.₅S sample produces a maximum photocatalytic H₂ production rate of 252.4 μmol h(-1). The junctions formed between metallic MoO₂ and semiconductor Zn₀.₅Cd₀.₅S by calcination play a key role in high photocatalytic water splitting to produce H₂. Our study demonstrates that metallic MoO₂ is an excellent H₂ evolution cocatalyst, and could be used as a cocatalyst for other semiconductors to improve performances.
由于基于半导体的纳米异质结构在当前电子学和光电子学中起着决定性的作用，因此引入有源异质结可以提供新的和改进的功能，从而提高太阳能向化学能的转化效率。在这项工作中，设计并制备了一种新型的金属/半导体 MoO₂/Zn₀.₅Cd₀.₅S 异质结，以显著提高光催化 H₂ 产生效率。通过可见光（λ≥420nm）照射下的水分解，测量了所制备的 MoO₂/Zn₀.₅Cd₀.₅S 用于 H₂ 产生的光催化活性。MoO₂/Zn₀.₅Cd₀.₅S 纳米粒子具有比 Zn₀.₅Cd₀.₅S 更高的光催化活性，即使没有贵金属共催化剂也是如此。结果表明，退火 MoO₂/Zn₀.₅Cd₀.₅S 的 H₂ 释放速率约是 Zn₀.₅Cd₀.₅S 单独的 13 倍，是简单混合的 MoO₂/Zn₀.₅Cd₀.₅S 的 10 倍。这意味着 MoO₂和 Zn₀.₅Cd₀.₅S 界面的强耦合促进了 Zn₀.₅Cd₀.₅S 的导带中的电子转移到金属 MoO₂，从而促进了光生电子和空穴的分离。在 673K 下煅烧的 MoO₂（2wt%）/Zn₀.₅Cd₀.₅S 异质结构光催化剂实现了 H₂ 释放的最佳整体活性。引入金属 MoO₂共催化剂可显著提高 Zn₀.₅Cd₀.₅S 的光电流和光催化 H₂ 产生活性，并且该催化剂中 MoO₂的含量对光催化活性有重要影响。结果表明，负载在 Zn₀.₅Cd₀.₅S 样品上的 2wt%金属 MoO₂产生了 252.4μmol h(-1) 的最大光催化 H₂产生速率。通过煅烧在金属 MoO₂和半导体 Zn₀.₅Cd₀.₅S 之间形成的结在高催化水分解产生 H₂中起着关键作用。我们的研究表明，金属 MoO₂是一种出色的 H₂ 析出共催化剂，并可用作其他半导体的共催化剂以提高性能。
