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

本文研究了氧化石墨烯负载Pt单原子(Pt₁/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Pt₁/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Pt₁/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16.1 kcal/mol. 因此，Pt₁/Gr-O有希望成为室温催化NH₃BH₃全水解催化剂.

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

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.