自由基修饰的黄铁矿表面催化性能的研究

Pyrite (FeS2) is the most abundant sulfide mineral in the world. The discovery of a reduced Fe(I)-S phase created by hydrogen-atom bombardment of an FeS2 surface has inspired research work on the catalytic activity of this surface, because the surface bears a structural similarity to the iron-sulfur center in FeMo-nitrogenases and FeFe-hydrogenases. In this project, we plan to study the potential catalytic activity of reduced pyrite surface for ammonia synthesis by using of Temperature Programmed Desorption(TPD) and Time of Flight technologies(TOF).At first,FeS2 is modified and and reduced by H atom or D atom. Then a beam of energetic nitrogen will be directed at hydrogenated and reduced pyrite surfaces, in the mean time, products scattered from surface will be monitored. The proposed work seeks to demonstrate unequivocally that the reduced iron-sulfur surface is an effective catalyst for nitrogen reduction and to gain insight into the details of the catalytic mechanism.The demonstration of significant catalytic activity on a reduced iron-sulfur surface, along with the initial mechanistic details to be uncovered via molecular beam scattering methods, would open a new area of research in the field of heterogeneous catalysis that could potentially lead to practical biomimetic catalysts for important reactions such as ammonia synthesis and carbon dioxide reduction.

黄铁矿(FeS2)是地壳中分布最广的硫化物,其表面经氢原子轰击后会产生还原性的Fe(I)-S相,此发现激发了关于FeS2表面的催化活性的研究,因为Fe(I)-S相 与FeMo-固氮酶和FeFe-氢化酶的铁硫活化中心具有相似的结构.本项目拟采用程序升温脱附谱（超声分子束-表面散射仪）和飞行时间谱方法（通用型交叉分子束装置），在FeS2表面进行还原氮气合成氨气的催化活性的研究。首先，采用H原子或D原子将FeS2表面还原修饰，然后将高能氮气束入射到被还原修饰的FeS2表面上，在原子分子水平上理解氮气在二硫化铁表面的还原机理，并研究与这一催化过程紧密相关的N2，H2，N原子，H原子，以及H2S与FeS2表面相互作用的动力学。该还原修饰的表面的催化活性以及其机理的研究将开启异相催化研究领域（如氨气合成，CO还原）产生实用仿生催化剂的新方向。

黄铁矿(FeS2)是地壳中分布最广的硫化物,其表面经氢原子轰击后会产生还原性的Fe(I)-S 相,此发现激发了关于FeS2 表面的催化活性的研究,因为Fe(I)-S 相 与FeMo-固氮酶和FeFe-氢化酶的铁硫活化中心具有相似的结构.本项目重点考查了与FeS2(100)上合成氨气相关的基元过程，特别是N原子和N2分子，H原子和H2分子，以及NH、NH2、NH3在黄铁矿FeS2(100)表面的吸附，研究了吸附物吸附在表面上的几何结构和吸附能。研究发现氮原子和氮气分子更倾向吸附在Fe原子的顶位，与氮气分子比较，氮原子的吸附更稳定，吸附能结果显示随着氮原子覆盖度的增加，吸附稳定性降低。氢原子能够稳定的吸附在Fe原子的顶位,吸附能随着覆盖度的增加而增加，表明随着氢原子覆盖度的增加，吸附稳定性降低。与氢原子的稳定吸附不同，氢气分子很难吸附在FeS2(100)表面上。以S为终止层的FeS2(100)表面上，NH吸附在空位上方，NH2、NH3吸附在Fe、S的桥位上方时最稳定，吸附稳定性顺序为NH > NH2 > NH3，以Fe为终止层的FeS2(100)表面上，NH、NH2、NH3中的N原子均是吸附在Fe的上方，吸附稳定性顺序为NH > NH2 > NH3。