Activating lattice oxygen of two-dimensional MnXn-1O2 MXenes via zero-dimensional graphene quantum dots for water oxidation  

零维石墨烯量子点活化二维MXenes的晶格氧参与水氧化反应

作　　者：Yiyuan Ma Yurong An Zhuo Xu Laifei Cheng Wenyu Yuan 马艺媛;安玉蓉;徐卓;成来飞;袁文玉(Science and Technology on Thermostructural Composite Materials Laboratory,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China;State Key Laboratory of Solidification Processing,School of Material Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China;Shaanxi Key Laboratory for Advanced Energy Devices,Shaanxi Engineering Lab for Advanced Energy Technology,Institute for Advanced Energy Materials,School of Materials Science and Engineering,Shaanxi Normal University,Xi’an 710119,China;Key Laboratory of Macromolecular Science of Shaanxi Province,Key Laboratory of Applied Surface and Colloid Chemistry,School of Chemistry&Chemical Engineering,Shaanxi Normal University,Xi’an 710062,China)

机构地区：[1]Science and Technology on Thermostructural Composite Materials Laboratory,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China [2]State Key Laboratory of Solidification Processing,School of Material Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China [3]Shaanxi Key Laboratory for Advanced Energy Devices,Shaanxi Engineering Lab for Advanced Energy Technology,Institute for Advanced Energy Materials,School of Materials Science and Engineering,Shaanxi Normal University,Xi’an 710119,China [4]Key Laboratory of Macromolecular Science of Shaanxi Province,Key Laboratory of Applied Surface and Colloid Chemistry,School of Chemistry&Chemical Engineering,Shaanxi Normal University,Xi’an 710062,China

出　　处：《Science China Materials》2022年第11期3053-3061,共9页中国科学（材料科学（英文版）

基　　金：supported by the National Natural Science Foundation of China(21901151 and 22071140);the Natural Science Foundation of Shaanxi Province(2020JQ-405 and 2021JLM-20);the Fundamental Research Funds from SNNU(1110011267 and 1112010334)。

摘　　要：The poor oxygen evolution reaction(OER)activity of two-dimensional(2 D)transition metal carbides(MXenes)is a major obstacle to their application in highperformance water splitting and fuel cells due to the high energy barriers for the absorption of intermediates.Here,we demonstrate that the lattice oxygen of M_(n)X_(n-1)O_(2)MXenes can be activated by 0 D graphene quantum dots(GQDs),thereby activating the OER via the lattice-oxygen oxidation mechanism(LOM)instead of the conventional adsorbate evolving mechanism.The pH-dependent OER activity of M_(n)X_(n-1)O_(2)@GQDs and ^(18)O isotope-labelling experiments with time-of-flight secondary-ion mass spectrometry(TOF-SIMS)provide the direct evidence of LOM.Interestingly,the activated lattice oxygen amount can be controlled by the GQDs.The as-prepared 0 D/2 D Ti_(3)C_(2)O_(2)@GQDs heterostructure delivers a highly reduced overpotential of 390 mV(bare Ti_(3)C_(2)O_(2):530 mV)at a benchmark current density of 10 mA cm^(-2).Through optimizing the thickness and the additional conductive substrate,the overpotential at 10 mA cm^(-2)decreases to 250 mV,while the Tafel slope is reduced to 39 mV dec^(-1);these values indicate the as-prepared heterostructure is superior to the state-of-the-art MXene-based OER catalysts.This work provides a new strategy to enhance the OER activity of M_(n)X_(n-1)O_(2)and extends the application of LOM from perovskite to MXenes.二维过渡金属碳化物(MXenes)对含氧中间产物的吸附能垒高,使得MXenes对产氧反应(OER)的活性差,因此阻碍着其在高性能水分解和燃料电池中的应用.本文中,我们发现引入零维石墨烯量子点(GQDs)的M_(n)X_(n-1)O_(2)@GQDs的OER活性具有明显的pH依赖性,且其相关性可通过石墨烯量子点来进行调控,^(18)O同位素标记-飞行时间二次离子质谱分析表明GQDs的引入显著提升了晶格氧参与OER的程度,证明了M_(n)X_(n-1)O_(2)MXenes的晶格氧可以被GQDs激活.在晶格氧被激活的情况下,M_(n)X_(n-1)O_(2)@GQDs的电催化OER动力学过程则由传统的吸附演变机制转变为晶格氧机制.在10 mA cm^(-2)的基准电流密度下,所制备的0D/2D Ti_(3)C_(2)O_(2)@GQDs异质结构的过电位被大幅降低至390 mV(纯Ti_(3)C_(2)O_(2)高达530 mV).进一步通过优化厚度和导电基底,在10 mA cm^(-2)电流密度下的过电位可被降低到250 mV,塔菲尔斜率被抑制到39 mV dec^(-1),该结果优于目前最先进的MXenes基OER催化剂和商用贵金属催化剂.本工作将晶格氧机制的应用范围从钙钛矿扩展到MXenes,也为提升M_(n)X_(n-1)O_(2)的OER活性提供了一种全新策略,对MXenes的材料设计和电催化机理的深入理解都有积极意义.

关 键 词：graphene quantum dots lattice-oxygen activation oxygen evolution reaction water splitting HETEROSTRUCTURE 

分 类 号：TQ426[化学工程]