Tuning the Catalytic Activity of Doped Graphene by Computational Design

气候变化和环境污染是本世纪人类面临的两大威胁。在过去的几十年里，越来越多的关注对健康和气候变化的严重影响，从燃料废气中的氮氧化物（NOx）的存在导致立法者在汽车发动机和发电站的NOx排放量的允许大幅减少。在此背景下，面对全球二氧化碳和氮氧化物排放量前所未有的增长，以及新出现的灾难性影响，该赠款提案旨在设计用于绿色催化的新型石墨烯基2D材料。工业催化是一个高度能源密集型的过程，需要获得日益减少的矿产资源，如贵金属和稀土金属。石墨烯是2004年发现的新的“奇迹2D材料”，可以提供一种解决方案，但纯石墨烯对于多相催化没有化学活性。这项研究提案背后的愿景是使用计算工具和建模来设计催化活性石墨烯基材料，其中活性位点的性质根据对CO2和NOx的所需化学活性进行调整。特别是，我们将研究化学掺杂的替代插入硼，氮和磷（B-，N-和P-掺杂），缺陷（单空位，SW空位和边缘），缺陷密度和应变的作用，对工业和环境的关键过程：1）减少氮氧化物（脱氮过程）; 2）封存和转化的二氧化碳。因此，该提议的具体目标可以概括如下：1）NOx的还原：在富含NOx的燃料气体排气的脱NOx处理中采用的当前技术通常需要越来越昂贵的贵金属，例如Pt、Pd和Rh。为了降低deNOx催化剂中活性金属相的浓度，通常将金属相制备为分散在惰性载体上或与无机氧化物结合成配位络合物的纳米颗粒。催化剂的制备提出了几个技术挑战，因为金属纳米颗粒用作无机载体、沸石和金属有机骨架上的活性位点，并且难以合成和以所需的尺寸、形状和浓度生长。替代催化剂，特别是基于活性2D碳材料的那些，提供了昂贵的传统催化剂的可行替代方案，因为它们本质上提供了高得多的表面积，非常坚固和灵活，并且可以由常见的有机化学品如烃、吡啶或氨制备（对于N掺杂的石墨烯）、膦或吡啶（对于P掺杂的石墨烯）。2）CO2的封存和转化：为了解决当前CO2排放和全球变暖的趋势，需要新的技术来限制产生的CO2的量并捕获来自能源过程的气体排放中所含的CO2。在过去的几年里，石墨烯因其在光催化材料中提高太阳能燃料发电效率的能力而引起了相当大的兴趣。基于石墨烯的技术已被证明可以促进将CO2还原为碳氢化合物和水。在这些新技术中，石墨烯有几个作用：从抑制电荷复合和增加光生电子和空穴的迁移，到直接催化分解CO2和产生CO2-xH 2x物质（CH 4，CH 2 O）和CH 3OH。在这项研究中，我们将研究掺杂和有缺陷的石墨烯上的CO2封存和转化机制，目的是设计最有前途的石墨烯功能改性，使其具有催化活性，同时保持更高的载流子迁移率。

Climate change and environmental pollution are two of the biggest threats faced by humankind in this century. In the past few decades, an increasing concern about the severe impact on health and climate change from the presence of nitrogen oxides (NOx) in fuel exhaust has led legislators to a drastic decrease in the permitted amount of NOx emissions from automotive engines and power stations. In this context, while facing an unprecedented global increase in CO2 and NOx emissions, with emerging catastrophic effects, this grant proposal aims at designing new graphene-based 2D materials for green catalysis.Industrial catalysis is a highly energy intensive process that requires access to diminishing mineral resources, such as precious and rare earth metals. Graphene, the new "Miracle 2D Material" discovered in 2004, could offer a solution, but pure graphene is not chemically active for heterogeneous catalysis. The vision behind this research proposal is to use computational tools and modelling to design catalytically active graphene-based materials in which the properties of the active sites are tuned according to the desired chemical activity toward CO2 and NOx. In particular, we will investigate the role of chemical doping by substitutional insertion of boron, nitrogen and phosphorus (B-, N- and P-doping), defects (single vacancies, SW vacancies and edges), defect densities and strain on industrially and environmentally critical processes: 1) the reduction of NOx (deNOx process); 2) the sequestration and conversion of CO2. The specific aims of this proposal can therefore be summarized as follows:1) Reduction of NOx: the current technology employed in deNOx treatment of NOx-rich fuel gas exhausts often requires increasingly expensive precious metals such as Pt, Pd and Rh. In order to reduce the concentration of the active metal phase in the deNOx catalysts the metal phase is often prepared as nanoparticles dispersed on an inert support or bound into coordination complexes with inorganic oxides. The catalyst preparation presents several technological challenges because the metal nanoparticles employed as active sites on inorganic supports, zeolites and metalorganic frameworks and are difficult to synthetize and grow in the desired size, shape and concentration. Alternative catalysts, in particular those based on activated 2D carbon materials, offer a viable alternative to costly traditional catalysts because they intrinsically offer much higher surface area, are extremely robust and flexible and can be prepared from common organic chemicals such as hydrocarbons, pyridine or ammonia (for N-doped graphene), phosphine or pyridine (for P-doped graphene).2) Sequestration and conversion of CO2: To address the current trend in CO2 emission and global warming requires novel technology to both limit the amount of CO2 produced and to capture the CO2 contained in the gas exhausts from energy processes. In the past few years, graphene has generated considerable interest for its capacity to increase the efficiency of solar-fuel generation in photocatalytic materials. Graphene based technology has been shown to promote the reduction of CO2 to hydrocarbons and water. In these novel technologies, graphene has several roles: from suppressing the charge recombination and increasing the migrations of photogenerated electrons and holes, to the direct catalytic dissociation of CO2 and production of CO2-xH2x species (CH4, CH2O) and CH3OH. In this research, we will investigate the mechanism of CO2 sequestration and conversion on doped and defective graphene with the aim of designing the most promising functional modification of graphene that would be catalytically active while simultaneously maintaining a higher carrier mobility.