Metal-doped Mo2C(metal=Fe,Co,Ni,Cu)as catalysts on TiO2 for photocatalytic hydrogen evolution in neutral solution  

金属(Fe,Co,Ni,Cu)掺杂的Mo2C催化剂在TiO2表面用于中性条件光催化分解水产氢

作　　者：Jing Liu Gary Hodes Junqing Yan Shengzhong(Frank)Liu 刘晶;盖瑞侯得;闫俊青;刘生忠(陕西师范大学,应用表面与胶体化学教育部重点实验室,陕西省能源新材料与器件重点实验室,陕西省能源新技术工程实验室,材料科学与工程学院,中国陕西西安710119;中国科学院大连化学物理研究所,中国科学院洁净能源创新研究院,能源材料化学协同创新中心(iChEM),中国辽宁大连116023;魏茨曼科学研究院,以色列雷霍沃特)

机构地区：[1]Key Laboratory of Applied Surface and Colloid Chemistry,Ministry of Education,Shaanxi Key Laboratory for Advanced Energy Devices,Shaanxi Engineering Lab for Advanced Energy Technology,School of Materials Science and Engineering,Shaanxi Normal University,Xi’an 710119,Shaanxi,China [2]iChEM,Dalian National Laboratory for Clean Energy,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,Liaoning,China [3]Department of Materials and Interfaces,Weizmann Institute of Science,Rehovot,76100,Israel

出　　处：《Chinese Journal of Catalysis》2021年第1期205-216,共12页催化学报（英文）

基　　金：国家重点研发计划(2017YFA0204800,2016YFA0202403);国家自然科学基金(21603136);长江学者和创新团队发展计划(IRT_14R33);高等学校学科创新引智计划(“111计划”,B14041).

摘　　要：The neutral hydrogen evolution reaction(HER)is vital in the chemical industry,and its efficiency depends on the interior character of the catalyst.Herein,work function(WF)engineering is introduced via 3d metal(Fe,Co,Ni,and Cu)doping for modulating the Fermi energy level of Mo2C.The defective energy level facilitates the free water molecule adsorption and,subsequently,promotes the neutral HER efficiency.Specifically,at a current density of 10 mA/cm2,Cu-Mo2C exhibits the best HER performance with an overpotential of 78 mV,followed by Ni-Mo2C,Co-Mo2C,Fe-Mo2C,and bare Mo2C with 90,95,100,and 173 mV,respectively,and the corresponding Tafel slope values are 40,43,42,56,and 102 mV/dec.The modified WF can also lead to an enhanced photocatalytic efficiency owing to the lowered Schottky barrier and excellent carrier transition across the electrocatalyst–solution interface.When coupling the metal-doped Mo2C samples with TiO2,enhanced photocatalytic neutral HER rates are obtained in comparison to the case with bare TiO2.Typically,the HER rates are 521,404,275,224,147,and 112μmol/h for Cu,Ni,Co,Fe,bare Mo2C,and bare TiO2,respectively.Time-resolved photoluminescence spectroscopy(TRPS)and ultrafast transient absorption(TA)measurements are carried out to confirm the recombination and migration of the photogenerated carriers.The fittedτvalues from the TRPS curves are 22.6,20.5,10.1,4.7,4.0,2.5,and 1.9 ns for TiO2,TiO2-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,and TiO2-Pt,respectively.Additionally,the fittedτvalues from the TA results are 31,73,and 105 ps for the TiO2-Mo2C,TiO2-Cu-Mo2C,and TiO2-Pt samples,respectively.This work provides in-depth insights into the WF modulation of an electrocatalyst for improving the HER performance.中性条件下的分解水产氢(HER)是化工领域的重要反应之一,其效率取决于催化剂的内在特性.在本工作中,我们利用3d金属(Fe,Co,Ni,Cu)对Mo2C进行掺杂来调节其费米能级,从而达到催化剂可在中性条件下吸附水并提高最终活性的目的.首先,利用简单浸渍法将四种金属的前驱体吸附到MoO3表面,然后通过煅烧一步合成金属掺杂的Mo2C.产物Mo2C的XRD峰位移以及XPS表征结果表明,四种金属通过掺杂进入到了Mo2C晶格.利用HRTEM以及相应的元素面扫分析,也证明金属确实掺杂进入了Mo2C体相.考察了Mo2C基催化剂在中性条件下电解水产氢的性能,结果表明,在10 mA/cm2条件下,Cu-Mo2C催化剂表现出最优的HER性能,其次,是Ni-Mo2C,Co-Mo2C,Fe-Mo2C和纯Mo2C,它们的过电位分别为78,90,95,100和173 mV,Tafel斜率分别是40,43,42,56和102 mV/dec.利用阻抗测试详细分析了催化剂-反应液界面电阻Rct的变化情况,样品Mo2C,Fe-Mo2C,Co-Mo2C,Ni-Mo2C和Cu-Mo2C拟合后的Rct值分别为119,89.6,46.5,33.8和23.2 ohm/cm^2,表明金属掺杂能明显降低催化剂的反应界面电阻.由于电催化过程的主要研究对象是表面双电层,所以我们利用循环伏安法计算了催化剂表面双电层的数值,得到上述五个样品的Cdl数值分别为0.047,0.06,0.1,0.16和0.24 F/cm^2,双电层的提高为催化剂表面提供了更多的反应位点.考虑了到光解水的界面反应实质也是电催化过程,我们通过浸渍方法将催化剂负载到锐钛矿TiO2表面,考察调控的功函数对光催化效率的影响.XPS表征验证了M-Mo2C负载于TiO2表面.负载助催化剂的TiO2-M-Mo2C样品均表现出了优于纯TiO2的光解水产氢性能.样品TiO2-Cu-Mo2C,TiO2-Ni-Mo2C,TiO2-Co-Mo2C,TiO2-Fe-Mo2C,TiO2-Mo2C和纯TiO2的产氢速率分别为21,404,275,224,147和112μmol/h.利用瞬态荧光研究了载流子在助催化剂和TiO2两相的界面迁移,通过单指数拟合得到样品TiO2,TiO2-Mo2C,TiO2-Fe-Mo2C,TiO2-Co-Mo2C,TiO2-Ni-Mo2C,T

关 键 词：3d metal Doping Mo2C TIO2 PHOTOCATALYSIS Water splitting Hydrogen evolution 

分 类 号：O643.36[理学—物理化学] TQ116.2[理学—化学] O644.1[化学工程—无机化工]