Department of Chemistry, University of Missouri - Kansas City , Kansas City, Missouri 64110, United States.
ACS Appl Mater Interfaces. 2017 Apr 26;9(16):14031-14042. doi: 10.1021/acsami.7b02701. Epub 2017 Apr 12.
The construction of exceptionally robust and high-quality semiconductor-cocatalyst heterojunctions remains a grand challenge toward highly efficient and durable solar-to-fuel conversion. Herein, novel graphitic carbon nitride (g-CN) nanosheets decorated with multifunctional metallic Ni interface layers and amorphous NiS cocatalysts were fabricated via a facile three-step process: the loading of Ni(OH) nanosheets, high-temperature H reduction, and further deposition of amorphous NiS nanosheets. The results demonstrated that both robust metallic Ni interface layers and amorphous NiS can be utilized as electron cocatalysts to markedly boost the visible-light H evolution over g-CN semiconductor. The optimized g-CN-based photocatalyst containing 0.5 wt % Ni and 1.0 wt % NiS presented the highest hydrogen evolution of 515 μmol g h, which was about 2.8 and 4.6 times as much as those obtained on binary g-CN-1.0%NiS and g-CN-0.5%Ni, respectively. Apparently, the metallic Ni interface layers play multifunctional roles in enhancing the visible-light H evolution, which could first collect the photogenerated electrons from g-CN, and then accelerate the surface H-evolution reaction kinetics over amorphous NiS cocatalysts. More interestingly, the synergetic effects of metallic Ni and amorphous NiS dual-layer electron cocatalysts could also improve the TEOA-oxidation capacity through upshifting the VB levels of g-CN. Comparatively speaking, the multifunctional metallic Ni layers are dominantly favorable for separating and transferring photoexcited charge carriers from g-CN to amorphous NiS cocatalysts owing to the formation of Schottky junctions, whereas the amorphous NiS nanosheets are mainly advantageous for decreasing the thermodynamic overpotentials for surface H-evolution reactions. It is hoped that the implantation of multifunctional metallic interface layers can provide a versatile approach to enhance the photocatalytic H generation over different semiconductor-cocatalyst heterojunctions.
构建异常坚固和高质量的半导体-助催化剂异质结仍然是实现高效和持久的太阳能到燃料转化的一大挑战。在此，通过简便的三步法制备了具有多功能金属 Ni 界面层和非晶态 NiS 助催化剂的新型石墨相氮化碳（g-CN）纳米片：负载 Ni(OH)纳米片、高温 H 还原和进一步沉积非晶态 NiS 纳米片。结果表明，坚固的金属 Ni 界面层和非晶态 NiS 均可作为电子助催化剂，显著提高 g-CN 半导体的可见光 H 演化。优化的含 0.5wt%Ni 和 1.0wt%NiS 的 g-CN 基光催化剂的产氢量最高，为 515μmol g h，分别是二元 g-CN-1.0%NiS 和 g-CN-0.5%Ni 的 2.8 和 4.6 倍。显然，金属 Ni 界面层在增强可见光 H 演化方面发挥了多种功能，可以从 g-CN 中首先收集光生电子，然后加速非晶态 NiS 助催化剂上的表面 H 演化反应动力学。更有趣的是，金属 Ni 和非晶态 NiS 双层电子助催化剂的协同效应也可以通过提高 g-CN 的 VB 水平来提高 TEOA 氧化能力。相对而言，多功能金属 Ni 层主要有利于通过形成肖特基结将光激发的电荷载流子从 g-CN 中分离并转移到非晶态 NiS 助催化剂中，而非晶态 NiS 纳米片主要有利于降低表面 H 演化反应的热力学过电势。希望多功能金属界面层的植入可以为增强不同半导体-助催化剂异质结的光催化 H 生成提供一种通用方法。
