石墨磷引起的缺陷碳纳米管展现出较高的氢析出活性

A correlation of the hydrogen evolution reaction activity to the number of defects formed by the decomposition of doped phosphorus species in carbon nanotubes

作为一种新型碳基析氢反应催化剂,磷掺杂炭材料近年来已引起了较大关注。然而到目前为止,磷掺杂炭材料中的C―P物种对于氢析出活性的作用尚未被揭示。为了探讨碳基催化剂中C―P物种对其氢析出性能的影响,制备了4种具有不同石墨、吡啶、吡咯类磷物种分布的磷掺杂碳纳米管,并探讨了这3种磷物种的含量和氢析出活性之间的关系。结果表明在酸性介质中,一种在电流密度为10 mA cm^(−2)时过电位为0.266 V的磷掺杂碳纳米管展现出较高的氢析出活性。同时,密度泛函理论计算表明较高的氢析出性能主要是由石墨磷分解产生的五元环和九元环缺陷所引起,这为磷掺杂碳基催化剂表面的析氢反应提供更为深入的理解。

Phosphorus-doped carbon materials are one of the novel carbon catalysts for the hydrogen evolution reaction(HER)that have attracted considerable attention in recent years.However,the role of C―P species played in the HER activity is still not clear.Phosphorus-doped carbon nanotubes were prepared by chemical vapor deposition and annealed at 900,1000 and 1200℃ to remove all or part of the phosporus,resulting in four samples with different amounts of substitutional-,pyridine-and pyrrole-like P species.The correlations between the HER activity and the contents of the three species were investigated.Results showed that the content of substitutional P decreased with annealing temperature and none was retained at 1200℃.The HER activity increased with annealing temperature and the sample annealed at 1200℃ had the highest HER activity in an acid medium with an overpotential of 0.266 V at a current density of 10 mA cm^(−2).Density functional theory calculations showed that the pentagon-and nine-membered ring defects formed by the elimination of substitutional P mainly contributed to the HER activity.