Constructing oxygen vacancy‐regulated cobalt molybdate nanoflakes for efficient oxygen evolution reaction catalysis  

构建氧空位调控的钼酸钴纳米片用于高效催化析氧反应

作　　者：Tingting Jiang Weiwei Xie Shipeng Geng Ruchun Li Shuqin Song Yi Wang 蒋婷婷;谢伟伟;耿仕鹏;李如春;宋树芹;王毅(中山大学化学工程与技术学院,广东省低碳化学与过程节能重点实验室,聚合物复合材料及功能材料教育部重点实验室,广东广州510275;中山大学材料科学与工程学院,广东广州510275)

机构地区：[1]The Key Lab of Low‐Carbon Chemistry&Energy Conservation of Guangdong Province,PCFM Lab,School of Chemical Engineering and Technology,Sun Yat‐sen University,Guangzhou 510275,Guangdong,China [2]School of Materials Science and Engineering,Sun Yat‐sen University,Guangzhou 510275,Guangdong,China

出　　处：《Chinese Journal of Catalysis》2022年第9期2434-2442,共9页催化学报（英文）

基　　金：国家自然科学基金(21975292,21978331,21905311,92061124);广州科技项目(201707010079);广东省基础与应用基础研究基金(2020A1515010343,2021A1515010167).

摘　　要：Oxygen evolution reaction(OER)is the dominant step for plenty of energy conversion and storage technologies.However,the OER suffers from sluggish kinetics and high overpotential due to its complex 4‐electron/proton transfer mechanism.Thus,developing efficient electrocatalysts is particularly urgent to accelerate OER catalysis but still remains a great challenge.Herein,we have synthesized the novel cobalt molybdate nanoflakes(CoMoO_(4)‐O_(v)‐n@GF)with adjustable oxygen vacancies contents by in situ constructing CoMoO_(4) nanoflakes on graphite felt(GF)and annealing treatment under the reduction atmosphere.The best‐performing CoMoO_(4)‐O_(v)‐2@GF with optimal oxygen vacancies content shows splendid electrocatalytic performance with the low overpotential(296 mV at 10 mA cm^(‒2))and also small Tafel slope(62.4 mV dec^(‒1))in alkaline solution,which are comparable to those of the RuO_(2)@GF.The experimental and the density functional theory calculations results reveal that the construction of optimal oxygen vacancies in CoMoO_(4) can expose more active sites,narrow the band‐gap to increase the electrical conductivity,and modulate the free energy of the OER‐related intermediates to accelerate OER kinetics,thus improving its intrinsic activity.析氧反应(OER)是金属-空气电池、电解水等绿色可再生能源转换与储存系统的核心反应,其复杂的4电子-质子耦合反应导致其动力学过程缓慢从而使得系统过电位较高,目前主要依赖于RuO_(2)或IrO_(2)贵金属催化剂提升其反应速率,但贵金属高成本和低稳定性严重限制其大规模应用.因此,开发高活性、高稳定性的廉价非贵金属催化剂具有重要的实际意义,已成为现阶段的研究热点.钼酸钴(CoMoO_(4))作为典型的ABO_(4)型催化材料,不仅价格低廉、储量丰富,而且其双金属特性可构筑有效的活性位点提升OER反应动力学.前期研究发现,通过阴离子掺杂、氧空位工程、电子结构调控、表面修饰等策略可增强ABO_(4)型催化剂的OER催化活性.特别是氧空位工程可调节过渡金属氧化物的电子结构,提高其导电性能,增加催化位点活性,从而提高过渡金属氧化物的催化性能.本文在石墨毡(GF)上原位生长CoMoO_(4)纳米片,并提出一种简单的H_(2)/Ar还原策略精确调控CoMoO_(4)的氧化状态,制备一系列不同氧空位含量的CoMoO_(4)电催化剂(CoMoO_(4)-O_(v)-n@GF),并采用X射线光电子能谱(XPS)、电子自旋共振(EPR)、电化学测试等表征手段及密度泛函理论计算(DFT)研究了氧空位含量对CoMoO_(4)电催化OER性能的影响.扫描电镜结果表明,花瓣状CoMoO_(4)纳米薄片整齐地生长在GF上,经还原热处理后纳米薄片结构未被破坏.透射电镜结果表明,经还原后CoMoO_(4)出现了大量缺陷,且显示出多晶的特性.XPS及EPR测试结果表明,通过改变热处理时间(0.5‒3 h)可以实现氧空位含量的精准调控,热处理时间越长,CoMoO_(4)氧空位含量越多.电化学测试结果表明,氧空位含量对CoMoO_(4)电催化OER性能起到了重要的调节作用,其中具有最优氧空位含量的CoMoO_(4)-O_(v)-2@GF表现出最佳的OER活性,在10 mA cm^(‒2)下的过电位仅为296 mV,Tafel斜率为62.4 mV dec^(−1),其性

关 键 词：Oxygen evolution reaction Oxygen vacancy Cobalt molybdate Nanoflake Density functional theory 

分 类 号：TQ426[化学工程] TB383.1[一般工业技术—材料科学与工程]