氧化石墨烯负载的Pt单原子催化硼胺烷水解机理的理论研究（英文）

Single Pt Atoms Supported on Oxidized Graphene as a Promising Catalyst for Hydrolysis of Ammonia Borane

本文研究了氧化石墨烯负载Pt单原子(Pti/Gr-O)催化硼胺烷(NH3BH3)全水解反应机理,即一分子的NH3BH3生成三分子的氢气(H2)的过程.在水解路径中,首先吸附的硼胺烷连续断裂两个B-H键生成第一分子的H2.接着,一个H2O分子与*BHNH3基团(*表示吸附态)反应生成*BH(H2O)NH3,其中伸长的O-H键断裂后形成*BH(OH)NH3.然后,第二个H2O与*BH(OH)NH3反应生成*BH(OH)(H2O)NH3,在指向Pti/Gr-O表面的O-H断裂后,生成BH(OH)2NH3并脱附到水溶液中.两个水分子脱氢产生的两个H原子脱附生成第二个H2分子,且Pti/Gr-O催化剂恢复.脱附后的BH(OH)2NH3在水溶液中水解生成第三个H2分子.纵观整个水解反应,H2O分子和*BHNH3基团的结合是反应速控步,其反应能垒是16.1kcal/mol.因此,Pti/Gr-O有希望成为室温催化NH3BH3全水解催化剂.

Based on density functional theory calculations,the full hydrolysis of per NH3BH3 molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene(Pt1/Gr-O)is investigated.It is suggested that the first hydrogen molecule is produced by the combination of two hydrogen atoms from two successive B-H bonds breaking.Then one H2O molecule attacks the left*BHNH3 group(*represents adsorbed state)to form*BH(H2O)NH3 and the elongated O-H bond is easily broken to produce*BH(OH)NH3.The second H2O molecule attacks*BH(OH)NH3 to form*BH(OH)(H2O)NH3 and the breaking of O-H bond pointing to the plane of Pt1/Gr-O results in the desorption of BH(OH)2NH3.The second hydrogen molecule is produced from two hydrogen atoms coming from two H2O molecules and Pt1/Gr-O is recovered after the releasing of hydrogen molecule.The third hydrogen molecule is generated by the further hydrolysis of BH(OH)2NH3 in water solution.The rate-limiting step of the whole process is the combination of one H2O molecule and*BHNH3 with an energy barrier of 16.1 kcal/mol.Thus,Pt1/Gr-O is suggested to be a promising catalyst for hydrolysis of NH3BH3 at room temperature.