CAS: 2D-WS2 Supported 2D-ZnO Nanoislands for Visible-Light-Driven Photocatalysis

南阿拉巴马大学的Arjun Dahal博士在化学系化学催化(CAT)计划和既定的刺激竞争研究计划(EPSCoR)的支持下，正在研究创新的异质结构光催化剂的设计，这种光催化剂有可能成为破坏性的光催化剂，用于环境友好和可持续的能源生产。在开发创新和绿色能源技术方面的科学突破可以使经济摆脱化石燃料，减少气候变化的影响。氢气是燃烧燃料中单位重量含能量最高的燃料，而且只产生水，因此被认为是一种很有前途的“绿色燃料”。利用太阳光和光催化剂材料分解水的光催化过程生产氢气是一种很有前途的清洁能源方法。设计创新的光催化剂是实现高效制氢的首要步骤。Dahal博士正在开发创新的、低成本的、潜在的高效异质结构光催化剂，其中包括二维(2D)金属氧化物和2D过渡金属二卤化物。作为该项目的一部分，Dahal博士还将研究异质结构的光催化效率与其尺寸、密度、化学成分和电子性质之间的相关性。该项目将为学生提供在现代能源和环境应用背景下培训尖端纳米科学的机会。拟议的研究具有很强的跨学科性质，向学生传授物理和化学概念，为学生进入高级学位课程和/或学术界和工业界的职业生涯做好更好的准备。在这个项目中，Dahal研究小组正在研究2D-ZnO和2D-WS2异质结的制备方法和生长机理。Dahal博士将实施物理气相沉积(PVD)方法，在使用化学气相沉积(CVD)方法制备的2D-WS2载体上生长2D-ZnO纳米岛。PVD是一种理想的方法，因为它能够控制异质结构的形态、尺寸、密度、化学成分和电子性质。Dahal博士将使用原子力显微镜来表征纳米结构的形态、大小和密度。光电子能谱将深入了解这些异质结构的化学成分和电子状态，而进行的测绘测量应能提供对界面质量的额外洞察。PVD和CVD生长方法有可能形成高质量的界面。Dahal和他的团队将通过测量有机染料溶液在紫外光/可见光照射下存在这些异质结构时的降解速度来评估光催化效率。该小组还将使用气相色谱技术直接量化光照射下水分解反应的放氢效率。由于协同效应，所提出的异质结构可能比传统的光催化剂更有效，因为它们可以提供更宽的捕光范围，使得电荷复合的可能性很低，并在暴露的表面提供许多活跃的反应位点。在更广泛的科学影响方面，该项目有可能提出一种使用2D金属氧化物和2D过渡金属二卤化物的新型光催化剂，并有望提供关于目标异质结构属性的有用信息，如结晶度、结晶度相、表面结构、带隙修改和缺陷。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Catalysis (CAT) program in the Division of Chemistry, and the Established Program to Stimulate Competitive Research (EPSCoR), Dr. Arjun Dahal of the University of South Alabama is studying designing of innovative heterostructure photocatalysts, which have the potential to become disruptive photocatalysts for environmentally benign and sustainable energy production. Scientific breakthroughs in developing innovative and green energy technologies can move economies away from fossil fuels, reducing the effects of climate change. Hydrogen possesses the highest energy content per weight among combustion fuels and produces only water as the product; therefore, hydrogen is regarded as a promising "green fuel." Hydrogen production from the photocatalysis process by splitting water utilizing sunlight and photocatalyst materials is a promising method of generating clean energy. Designing innovative photocatalysts is the primary step to realize efficient hydrogen production. Dr. Dahal is developing innovative, low-cost, and potentially highly efficient heterostructure photocatalysts comprising two-dimensional (2D) metal oxides and 2D transitional metal dichalcogenides. As part of the project, Dr. Dahal will also examine the correlation between the photocatalytic efficiency of the heterostructures to their size, density, chemical composition, and electronic properties. The project will offer opportunities to train students in cutting-edge nanoscale science within the context of modern energy and environmental applications. The proposed research is strongly interdisciplinary and teaches students physics and chemistry concepts that better prepare students for entry into advanced degree programs and/or careers in academia and industry. In this project, the Dahal research group is studying fabrication methods and growth mechanisms of heterostructures incorporating 2D-ZnO and 2D-WS2. Dr. Dahal will implement the physical vapor deposition (PVD) approach to grow 2D-ZnO nanoislands on the 2D-WS2 support prepared using the chemical vapor deposition (CVD) method. PVD is a desirable method because it enables the control over morphology, size, density, chemical composition, and electronic properties of the heterostructures. Dr. Dahal will characterize nanostructure morphology, size, and density using atomic force microscopy. Photoemission will give insight into the chemical composition and electronic states of these heterostructures, and the conducting mapping measurements should provide additional insight into the quality of the interfaces. The PVD and CVD growth methods have the potential to enable the formation of high-quality interfaces. Dahal and his team will evaluate the photocatalytic efficiency by measuring the rate of degradation of an organic dye solution in the presence of these heterostructures under UV/visible irradiation. The group will also directly quantify hydrogen evolution efficiency from water-splitting reactions under light irradiation using the gas chromatography technique. Due to the synergistic effects, the proposed heterostructures can potentially be more efficient than conventional photocatalysts because they can offer a wider light-harvesting range, enable a low probability of charge recombination, and provide many active reaction sites on exposed surfaces. In terms of broader scientific impact, this project has the potential to bring forward a new class of photocatalysts using 2D metal oxides and 2D transition metal dichalcogenides and is expected to provide useful information on the properties of the target heterostructures such as crystallinity, crystallinity phases, surface structures, band gap modifications, and defects.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.