摘要
Polymeric carbon nitride(PCN)is identified as a promising photocatalyst for H_(2)O_(2) production due to its visible-light response,low cost,and high selectivity of 2e^(-) oxygen reduction reaction(ORR).However,the H_(2)O_(2) yield of carbon nitride is still restricted by narrow light absorption,low charge separation efficiency,and insufficient active sites.Herein,crystalline poly(heptazine imide)(PHI)-based carbon nitride with highly dispersed In sites and N defects was prepared through the ionothermal method using LiCl/KCl as molten salts.The largeπ-conjugated system and the existence of N defects greatly enhance the visible-light harvesting ability.The remaining K^(+) ions in the nitrogen cavities of PHI serve as interlayer electron channels,and the incorporation of N defects triggers asymmetric distribution of charges on the heptazine network,promoting interlayer and in-plane charge separation and transfer,respectively.The In sites accelerate charge transfer dynamics and act as active sites for ORR.The synergistic effect of metal modification and defect engineering boosts the electron delocalization within the photocatalyst and thus significantly improves the photocatalytic activity.The H_(2)O_(2) production rate of 10InPHI reaches 15.3 mmol g^(-1)h^(-1)through a two-step single-electron ORR pathway,underscoring the great potential of modified carbon nitride materials in efficient H_(2)O_(2) photosynthesis.
聚合氮化碳因具有可见光响应能力、低成本以及高的两电子氧还原反应(ORR)选择性等优势,被认为是一种极具潜力的合成过氧化氢(H_(2)O_(2))的光催化剂.然而,受限于其光吸收范围窄、电荷分离效率低以及活性位点少等因素,当前聚合氮化碳产H_(2)O_(2)的产率仍不理想.本研究以LiCl/KCl为熔盐,通过离子热法制备了含有高度分散的铟(In)位点和氮缺陷的高结晶聚七嗪酰亚胺(PHI)基氮化碳材料.其较大的π共轭体系和引入的氮缺陷共同作用,显著增强了材料的可见光吸收能力.PHI框架中残留的K^(+)离子充当了层间电子传递通道,而氮缺陷的引入则导致七嗪网络中电荷分布不对称,两者分别促进了层间和面内的电荷分离与传输过程.引入的In位点不仅加速了电荷转移动力学,还作为ORR的活性位点.金属掺杂与缺陷工程的协同效应增强了光催化剂的电子离域程度,从而显著提升了其光催化活性.10InPHI催化剂通过两步单电子ORR途径,实现了高达15.3mmolg^(-1)h^(-1)的H_(2)O_(2)生成速率,展示出改性氮化碳材料在高效光合成H_(2)O_(2)反应中的巨大潜力.
基金
supported by the National Natural Science Foundation of China (22278056, 22478058)
the Fundamental Research Funds for the Central Universities (DUT22LAB602)
the National Key Research and Development Program of China (2022YFA1504402)。
