CAREER: Advanced Photochemical Paradigms for Enhanced Photovoltaics and Photocatalysis

X1150617智能优点太阳能转换和利用可以通过光电化学(PEC)计划实现，该计划将光能转换为电能，如基于PEC的光伏(PV)，或化学能源，如太阳能燃料和使用光催化剂的太阳能环境净化。因此，了解定义和调控PEC系统中基本光捕获和电荷传输过程的基础科学对于PEC太阳能电池和光催化的发展至关重要。这项提议的总体目标是从根本上改变和提高当前最先进的基于PEC的光伏和光催化系统中的初级光收集和电荷传输效率。具体地说，拟议的研究计划将针对以下分任务1。将传统PEC太阳能电池的光阳极(通常以平面透明导电氧化物(TCO)上的厚PV层的形式)转换为一组三维纳米结构的共形TCO/PV光阳极。这一创新将大大缩短光伏层中的传输长度，将大部分传输留在近乎金属的TCO层中，以增强光电流收集，同时仍提供足够的光伏材料来适应太阳光子通量。PI将研究由这些变革性结构产生的基本传输机制。特别是，将光伏层的厚度减小到TCO/PV层界面处的空间电荷层宽度(通常为30 nm)附近，可能会使整个光致电荷分离和传输过程受到该界面处内置电势的强烈影响。因此，慢扩散输运机制可以被更有效的场驱动漂移输运机制取代，以抑制光伏层中的电荷复合。反过来，可以应用具有较小过电位的替代更快的氧化还原介体来增强光伏性能。2.协同作用是，从二维到三维TCO的转变使得各种三维光子晶体(PC)构型可以结合到三维共形TCO/PV结构中，这种结构可以通过光子的多次散射来捕获光，导致光收集和电荷传输过程之间的协同而不是冲突。因此，PEC太阳能电池可以更实惠，因为需要更少的光伏材料来适应太阳能通量。3.自掺杂Ti3+和/或氧空位的TiO2x可以成为一种高效的可见光活性光催化剂，不需要额外的掺杂剂，从而最大限度地减少了对环境的影响。为了实现有效的可见光活动，Ti3+的浓度必须足够高，才能在TiO2导带边缘下方诱导出连续的电子态空位带。与传统的Ti4+-Ti3+在苛刻条件下还原不同，我们提出了一种以TiH2和H2O2为前驱体的Ti2+-Ti3+氧化转化方案，用于Ti3+自掺杂Ti3+光催化剂。这一过程将提供一种简单、低成本和高浓度掺杂Ti3+贯穿整个TiO2x基质的方法。TiH_2和H_2O_2反应生成水解型溶胶-凝胶型前驱体TiO2x，便于等离子体纳米粒子的掺入，形成多功能纳米结构的TiO2x，从而提高太阳光催化活性。更广泛的影响由于纳米科学为更有效的PEC过程提供了更多的机会，主要的教育目标是将与本项目和本科生化学相关的入门纳米科学实验整合到我们现有的课程和实验室作业中，以便向学生提供课程工作和基本纳米科学知识的动手理解。其次，作为培养下一代科学家的有效方式，PI计划通过开发一个多功能项目：阿尔贡北方学生科学家来扩大与阿贡科学家的研究合作。该计划将把PI与Argonne的研究合作纳入到招生、教育和培训、研究、就业和社区推广中。这些学生将接触到世界级的研究环境，从小参与前线研究项目，并接受尖端研究设施、跨学科知识、批判性思维和解决问题的方法以及团队合作技能的培训。由于石油和核能引发的环境灾害日益受到人们的关注，PEC能源转换成为能源科学中一个极具吸引力的方面。由于能源科学是Argonne的核心研究领域，PI将利用Argonne的研究和NIU的网络，通过Argonne和北伊利诺伊大学的科学家的互动演讲，为当地高中的学生和教师建立一个外展项目--能源和环境研讨会。

Xu1150617 Intellectual MeritsSolar energy conversion and utilization can be implemented through photoelecrochemical (PEC) schemes that convert light energy to electricity, such as PEC-based photovoltaics (PV), or chemical energy such as solar fuels and solar environmental purification using photocatalysts. Therefore, understanding the basic science that defines and regulates the elementary light harvesting and charge transport processes in PEC systems is crucial for the advancement of PEC solar cells and photocatalysis. The overall goal of this proposal is to fundamentally transform and enhance the elementary light harvesting and charge transport efficiencies in current state-of-the-art PEC-based photovoltaic and photocatalytic systems. Specifically, the proposed research plan will aim to the following subtasks.1. Converting the photoanodes of conventional PEC solar cells, typically in the format of a thick PV layer on a planar transparent conducting oxide (TCO), to a set of 3-D nanoarchitectured conformal TCO/PV photoanodes. This innovation will drastically shorten the transport length in the PV layer, leaving the majority of the transport in the nearly metallic TCO layer for enhanced photocurrent collection, while still providing sufficient PV material to accommodate the solar photon flux. The PI will study the fundamental transport mechanisms resulting from these transformative structures. In particular, reducing the thickness of the PV layer to approximately the width of the space charge layer (typically 30 nm) at the interface of TCO/PV layer can subject the overall light-induced charge separation and transport processes to the strong influence of the built-in potential at this interface. As a result, the slow diffusive transport mechanism can be replaced by the more efficient field-driven drift transport mechanism to suppress charge recombination in the PV layer. In turn, alternative faster redox mediators with less overpotential can be applied for enhanced photovoltaic performance. 2. Synergistically, the transformation from 2-D to 3-D TCO enables the incorporation of a variety of 3-D photonic crystal (PC) configurations into the 3-D conformal TCO/PV architectures, which can trap light through multiple scattering of photons, resulting in synergy rather than conflict between the light harvest and charge transport processes. As such, PEC solar cells can be more affordable since less PV materials are needed for accommodating the solar flux. 3. Ti3+ and/or oxygen vacancy self-doped TiO2-x can be an effective visible-light active photocatalyst that using no additional dopants, thus to minimize the environmental concerns. In order to achieve efficient visible-light activity, the concentration of Ti3+ must be high enough to induce a continuous vacancy band of electronic states just below the conduction band edge of TiO2. Distinguished from the conventional reduction of TiO2 (Ti4+-¨Ti3+) under harsh conditions, we propose an oxidative conversion (Ti2+-¨Ti3+) scheme that uses TiH2 and H2O2 as precursors for Ti3+ self-doped TiO2-x photocatalysts. This process will provide a facile, low-cost and high-concentration doping of Ti3+ throughout bulk of the TiO2-x matrix. The reaction of TiH2 and H2O2 produces a hydrolyzed sol-gel-like precursory TiO2-x, allowing convenient incorporation of plasmonic nanoparticles and formation of versatile nanoarchitectured TiO2-x for enhanced solar photocatalytic activity. Broader ImpactsAs nanoscience provides more opportunities for more efficient PEC processes, the primary educational goal is to integrate introductory nanoscience experiments relevant to both this project and undergraduate chemistry into our existing curriculum with laboratory assignments, so as to provide students hands-on understanding in course work and basic nanoscience knowledge. Secondly, as an effective way to train the next generation scientists, the PI plans to broaden the research collaboration with Argonne scientists by developing a multifunctional program: Northern Student Scientists at Argonne. This program will incorporate PI's research collaborations with Argonne into student recruitment, education and training, research, employment and community outreach. The students will be exposed to world-class research environment, involved in frontline research projects at their young age, and trained with cutting-edge research facilities, cross-disciplinary knowledge, critical thinking and problem-solving methodologies, and team-work skills. Due to the growing concerns on environmental disasters related to petroleum and nuclear energy, PEC energy conversion becomes a highly attractive aspect of energy science. As energy science is Argonne's core research area, the PI will leverage Argonne'fs research and NIU's network to establish an outreach program Energy and Environment Workshop for students and teachers in local high schools via interactive presentations given by scientists at Argonne and Northern Illinois University.