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。可持续的氢基经济需要从质子介质（如H2O或无机酸（HX））中生产氢，并与太阳能相结合。用于从质子介质将太阳能转化为氢的封闭催化循环必须满足两个技术障碍：1）质子还原以产生二氢，以及2）阴离子氧化。用于从HX产生H2的闭合循环需要质子还原以形成H2以及卤化物氧化以产生X2。到目前为止，还没有开发出用于真正的HX裂解的分子催化剂。已经开发了采用化学阱来促进X2形成的概念验证系统，然而，这些系统不适合用于能量存储。该提议旨在开发基于地球丰富的第一行过渡金属的用于光化学HX裂解的廉价催化剂。如果成功，拟议的研究将构成一个封闭的太阳能到氢转化方案，其中无机酸（HX）转化为H2和X2使用太阳能。所得到的氢可以用作燃料，或者通过氢化小分子底物如CO2作为液体燃料封存，或者直接用于氢燃料电池。为了实现开发太阳能制氢方案的目标，将首先开发能够还原质子的低价过渡金属络合物。同时，金属二卤化物配合物的调查将允许确定卤化物氧化的关键要求。为了实现具有挑战性但必要的X2光消除，将设计配体以提供对高度氧化激发态的接近。HX分裂的每个基本步骤的研究-质子还原和卤化物氧化-将阐明每个组成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实的HX裂解 要实现的目标。 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，城市环境中的主要来源是汽车尾气的颗粒空气污染每年造成50万人死亡。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.