自牺牲法合成氮空位g-C_(3)N_(4)/Cu_(2)(OH)_(2)CO_(3)异质结及其广谱光固氮性能

Efficient Wide-spectrum-driven N_(2)Photofixation over g-C_(3)N_(4)/Cu_(2)(OH)_(2)CO_(3)Heterojunction Doped of Nitrogen Vacancies via Self-sacrificial Method

本研究采用原位自牺牲法合成了N空位掺杂的g-C_(3)N_(4)/Cu_(2)(OH)_(2)CO_(3)(VCN/Cu)异质结催化剂,该催化剂体现出优异的可见-近红外宽光谱驱动性。实验结果表明,g-C_(3)N_(4)与Cu_(2)(OH)_(2)CO_(3)之间的电荷迁移遵循“Z”型机制。氮空位的存在抑制了电荷载流子的重组,降低了界面电荷转移的能量屏障,对N 2和O_(2)的吸附和活化激发了固氮还原反应的进行,并提供了更多的反应活性位点。体系中甲醇作为空穴清除剂时O_(2)的添加对制备的催化剂的光固氮性能有显著的促进作用,在50%O_(2)和50%N_(2)混合气氛下VCN/Cu异质结催化剂的铵离子产率高达14.52 mg·L^(-1)·h^(-1)·g^(-1),是纯N 2气氛下的2.7倍,且按照“三线”光固氮机理运行。本研究为低耗、绿色环保固氮工艺提供了一条新途径。

In this study,N vacancies-doped g-C_(3)N_(4)/Cu_(2)(OH)_(2)CO_(3)(VCN/Cu)heterojunction catalyst with superior wide-spectrum-driven(from VIS to NIR)N_(2)photofixation ability was synthesized via in-situ self-sacrificial method.The experimental results show that the charge transfer between g-C_(3)N_(4)and Cu_(2)(OH)_(2)CO_(3)follows the‘Z-scheme’mechanism.N vacancies-induced defect states might act as the initial charge carriers acceptor to reduce electron/hole recombination,and also promote the interfacial charge transfer from N vacancies of excited g-C_(3)N_(4)to N_(2)and O_(2)molecules absorbed and pre-activated by N vacancies,leading more active sites.The nitrogen photofixation performance of as-prepared catalyst is deeply influenced by the O_(2)content in reaction system with methanol as hole scavenger.The as-prepared VCN/Cu heterojunction catalyst demonstrates the ammonium ion production rate as high as 14.52 mg·L^(-1)·h^(-1)·g^(-1)under the atmosphere of 50%O_(2)and 50%N_(2),which is 2.7 times higher than that under pure nitrogen atmosphere,and a‘three-channel’ammonia production mechanism is proposed.This study might open up a new vista to nitrogen fixation through the less energy-demanding green photocatalytic process.