Earth-Abundant Transition Metal Catalysts for HX Splitting

描述(由申请人提供)：确定和实施清洁、可持续和负担得起的能源对未来的环境和人类健康问题至关重要。可持续的氢基经济要求质子化介质(如H2O或无机酸(HX))与太阳能耦合生产氢气。从质子介质中将太阳能转化为氢能的封闭催化循环必须满足两个技术障碍：1)质子还原生成氢气；2)阴离子氧化。从HX生成H2的闭合循环既需要质子还原生成H2，也需要卤化物氧化生成X2。到目前为止，还没有开发出真正用于裂解HX的分子催化剂。使用化学陷阱促进X2形成的概念验证系统已经开发出来，然而，这些系统不适合用于能量储存。这项提议旨在开发基于富含地球的第一排过渡金属的廉价催化剂，用于HX的光化学分解。如果成功，这项拟议的研究将构成一个封闭的太阳能到氢气转换计划，利用太阳能将无机酸(HX)转化为H2和X2。生成的氢可以用作燃料，既可以通过二氧化碳等小分子底物的氢化将其作为液体燃料进行隔离，也可以直接用于氢燃料电池。为了实现开发太阳能到氢气方案的目标，将首先开发能够质子还原的低价过渡金属络合物。同时，对金属二卤化物络合物的研究将使卤化物氧化的关键要求得以确定。为了实现具有挑战性但必要的X2光消除，配体将被设计成提供进入高度氧化的激发态的途径。对HX裂解的每个基本步骤--质子还原和卤化物氧化--的研究将阐明每个组分半反应所需的基本参数。根据HX裂解的每个基本步骤所需的配体特征，过渡金属催化剂将被设计成能够实现真正的HX裂解 光催化作用有待实现。 公共卫生相关性：确定和实施清洁、可持续和负担得起的能源对未来的环境和人类健康问题至关重要。2005年，据估计，每年造成50万人死亡的原因是颗粒物空气污染，其在城市环境中的主要来源是汽车尾气。在此，我建议开发用于HX裂解的新型过渡金属催化剂，这将使无污染的氢基燃料的使用成为可能，并切断能源和石油基燃料之间的联系。

DESCRIPTION (provided by applicant): Identification and implementation of clean, sustainable, and affordable energy sources is of paramount importance for both environmental and human health concerns in the future. Sustainable hydrogen-based economies require that hydrogen production from protic media, such as H2O or mineral acids (HX), be coupled to solar power. Closed catalytic cycles for solar-to-hydrogen energy conversion from protic media must meet two technological hurdles: 1) proton reduction to generate dihydrogen, and 2) anion oxidation. A closed cycle for generating H2 from HX requires both proton reduction to form H2 as well as halide oxidation to generate X2. Thus far, molecular catalysts for authentic HX splitting have not been developed. Proof-of-concept systems, which employ chemical traps to promote X2 formation have been developed, however, these systems are not amenable to use in energy storage. This proposal aims to develop inexpensive catalysts based on earth- abundant, first-row transition metals for photochemical HX splitting. If successful, the proposed research would constitute a closed solar-to-hydrogen conversion scheme, in which mineral acids (HX) are converted to H2 and X2 using solar power. The resultant hydrogen could be used as fuel, either by sequestration as a liquid fuel by hydrogenation of small molecule substrates such as CO2 or by being used directly in hydrogen fuel cells. To accomplish the goal of developing a solar-to-hydrogen scheme, low-valent transition metal complexes, capable of proton reduction will first be developed. Simultaneously, investigations of metal dihalide complexes will allow critical requirements for halide oxidation to be defined. To enable the challenging, but necessary, X2 photoelimination, ligands wil be designed to provide access to highly oxidizing excited states. Studies of each of the fundamental steps of HX splitting - proton reduction and halide oxidation - will elucidate fundamental parameters required for each of the constituent half reactions. Informed by the requisite ligand features for each of the fundamental steps of HX splitting, transition metal catalysts will be designed to enable authentic HX splitting photocatalysis to be achieved. PUBLIC HEALTH RELEVANCE: Identification and implementation of clean, sustainable, and affordable energy sources is of paramount importance for both environmental and human health concerns in the future. In 2005 it was estimated that particulate air pollution, whose major source in urban environments is automobile exhaust, is to blame for 500,000 deaths each year. Herein, I propose the development of novel transition metal catalysts for HX splitting, which would enable use of non-polluting hydrogen-based fuels and sever the connection between energy and petroleum-based fuels.