C₃N₄负载Ru催化氨硼烷水解产氢性能研究

Ru/C₃N₄ Catalysts for Hydrogen Generation via Hydrolysis of NH₃BH₃

摘要: 采用浸渍化学还原法制备氮化碳负载Ru催化剂，考察了还原剂NaBH₄用量、活性组分Ru的负载量等催化剂制备条件及转速、催化剂用量、反应温度等反应条件对Ru/C₃N₄催化剂催化NH₃BH₄水解产氢性能的影响。结果表明，在活性组分前体RuCl₃与还原剂NaBH₄物质的量比为1:5，活性组分Ru的负载量为0.4 wt.%，催化剂用量为0.05 g，Ru/C₃N₄催化剂催化氨硼烷水解产氢的TOF为227.8 mol H₂•mol⁻¹Co•min⁻¹。反应温度越高，反应物及产物传质越快，氨硼烷活化分子数目越多，氨硼烷产氢速率越快。催化剂用量越多，Ru活性位越多，氨硼烷产氢的速率越快；当转速为810 r/min，外扩散限制消除，氨硼烷产氢速率最快。Ru/C₃N₄催化剂催化氨硼烷水解产氢的活化能为39.20 kJ/mol，说明Ru/C₃N₄催化氨硼烷水解产氢速率受温度影响极小。

Abstract: C₃N₄ supported Ru catalysts were synthesized with an impregnation-reduction method. The prepared catalysts were evaluated for the hydrogen generation via catalytic hydrolysis of BH₃NH₃. Effect of catalytic activity was investigated by varying the impregnated Ru loading, amount of NaBH₄ as reducing agent during the preparation procedure, and was studied under different reaction conditions, such as reduction temperature, amount of used catalyst as well as the stirring speed. It was found that the TOF of 227.8 mol H₂•mol⁻¹Ru•min⁻¹ was achieved by using 0.05 g of Ru/C₃N₄ with Ru loading of 0.4 wt.%, while the molar ratio of RuCl₃:NaBH₄ was 1:5. Notably, with increasing reaction temperature, mass transfer of reactant and product was accelerated, and more BH₃NH₃ molecules were activated, leading to higher rate of hydrogen generation. In addition, more active sites of Ru were exposed with enhancing the amount of used catalyst, resulting in the enhancement of the reaction rate towards hydrogen formation as well. When the stirring speed was raised up to 810 r/min, external diffusion could be eliminated, leading to the highest reaction rate towards hydrogen generation. According to the kinetic study, the activation energy for hydrolysis of BH₃NH₃ towards hydrogen generation over Ru/C₃N₄ is 39.2 kJ•mol⁻¹. This indicates that the reaction temperature has almost no effect on catalytic activity towards hydrogen generation.