六氟钽酸氨拓扑转变制备低深能级缺陷Ta_(3)N_(5)光阳极实现超低偏压光电化学分解水  

A Ta_(3)N_(5)photoanode with few deep-level defects derived from topologic transition of ammonium tantalum oxyfluoride for ultralow-bias photoelectrochemical water splitting

作　　者：徐伟 甄超[1,2] 朱华泽[1,2] 姚婷婷 邱建航 梁艳 白朔 陈春林[1,2] 成会明 刘岗[1,2] Wei Xu;Chao Zhen;Huaze Zhu;Tingting Yao;Jianhang Qiu;Yan Liang;Shuo Bai;Chunlin Chen;Hui-Ming Cheng;Gang Liu(Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,Liaoning,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,Liaoning,China;Shi‐Changxu Innovation Center for Advanced Materials,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,Liaoning,China;Institute of Technology for Carbon Neutrality,Shenzhen Institute of Advanced Technology,Chinese Academy of Sciences,Shenzhen 518055,Guangdong,China)

机构地区：[1]中国科学院金属研究所,沈阳材料科学国家实验室,辽宁沈阳110016 [2]中国科学技术大学材料科学与工程学院,辽宁沈阳110016 [3]中国科学院金属研究所,师昌绪先进材料创新中心,辽宁沈阳110016 [4]中国科学院深圳先进技术研究院,碳中和技术研究所,广东深圳518055

出　　处：《Chinese Journal of Catalysis》2024年第6期144-153,共10页催化学报（英文）

基　　金：国家自然科学基金项目(52425201,52072377,52188101);国家重点发展计划项目(2021YFA1500800);中国科学院青年创新促进会项目(2020192);中国科学院青年基础研究项目(YSBR-004);新基石科学基金(科学探索奖).

摘　　要：Ta_(3)N_(5)是一种具有2.1 eV直接带隙的n型半导体,其带隙跨越水的氧化还原电位.此外,Ta_(3)N_(5)的理论太阳能制氢效率(STH)高达15.9%,超过商业化应用的效率门槛(10%),是一种理想的光电化学分解水制氢光阳极材料.采用Ta2O5作为前驱体,在氨气气氛下高温氮化制备Ta_(3)N_(5)是一个由表及里的非均相氮化过程,该过程会产生大量的低价钽和氮空位等本征深能级缺陷,导致费米能级钉扎效应的产生,从而使得光生电压显著降低和光电流起始电位较高.因此,开发能够进行体相均相氮化的前驱体,以抑制Ta_(3)N_(5)深能级缺陷的产生,具有重要意义.本文采用气相溶剂热法,在钽箔上制备了一种六氟钽酸氨((NH_(4))_(2)Ta_(2)O_(3)F_(6))化合物,并以其多面体锥阵列薄膜作为前驱体,通过可控的氮化过程将前驱体结构拓扑转变为低深能级缺陷含量的Ta_(3)N_(5)多孔阵列薄膜.在高温氮化过程中,(NH_(4))_(2)Ta_(2)O_(3)F_(6)会释放含氮、氢和氟的气体小分子并形成贯穿体相的多孔通道,有利于氨气及氮化过程中产生的其他小分子物质的渗透,促进体相均匀氮化过程,避免生成大量的本征深能级缺陷.同时,(NH_(4))_(2)Ta_(2)O_(3)F_(6)中的高电负性氟离子可以减弱Ta–O键,进一步促进氮化反应.扫描电镜和透射电镜(TEM)结果表明,制备的(NH_(4))_(2)Ta_(2)O_(3)F_(6)是具有实心结构的多面体锥阵列薄膜,而拓扑转变所得的Ta_(3)N_(5)多面体锥薄膜具有多孔结构.X射线光电子能谱(XPS)、紫外-可见漫反射光谱和稳态/瞬态光电压谱表征结果表明,通过(NH_(4))_(2)Ta_(2)O_(3)F_(6)拓扑转变制备Ta_(3)N_(5)可有效抑制Ta_(3)N_(5)薄膜中深能级缺陷的形成.采用两种产氧反应助催化剂依次修饰后,XPS和TEM结果显示出助催化剂的双壳层结构与化学组成.光电化学分解水测试结果表明,所制得的Ta_(3)N_(5)光阳极在AM1.5G模拟太阳光的照射下,可展现出0.2 V_(RHE)(An open challenge for developing solar-driven Ta_(3)N_(5)-based photoanodes with the ability to induce low-bias photoelectrochemical(PEC)water splitting is that their deep-level defects originated from low-valent tantalum cations(Ta^(3+))and nitrogen vacancies(VN)seriously reduce the photovoltage and thus increase the bias for water splitting.Herein,we developed an effective topotactic transition synthesis route of producing few deep-level defects porous Ta_(3)N_(5)film from the precursor film of ammonium tantalum oxyfluoride compound((NH_(4))_(2)Ta_(2)O_(3)F_(6))pyramids on the Ta foil.The highly electronegative fluoride ions in(NH_(4))_(2)Ta_(2)O_(3)F_(6)could weaken the Ta–O bonds and the accompanied porous structure facilitates reactant diffusion,which favors the complete nitridation.Consequently,the resulting porous Ta_(3)N_(5)film has very few deep-level defects,enabling an ultralow photocurrent onset potential at 0.2 V(vs.RHE)and a short-circuit photocurrent density(Jsc)of 3.28 mA cm^(–2) after decorating oxygen evolution reaction(OER)cocatalysts under AM 1.5 G irradiation.Moreover,the Jsc can retain 85%of the initial value for a 5 h continuous stability test.By reducing the particle size of(NH_(4))_(2)Ta_(2)O_(3)F_(6)pyramid precursor,the deep-level defects could be further lowered in the Ta_(3)N_(5)film,achieving the photoactivity for water oxidation at 0 V(vs.RHE)after modifying the OER co-catalyst.

关 键 词：(NH_(4))_(2)Ta_(2)O_(3)F_(6) 拓扑转变 低缺陷Ta3N5 起始电位 光电化学分解水 

分 类 号：TQ116.2[化学工程—无机化工] O643.36[理学—物理化学]