摘要
甘油是生物质精炼的主要副产物(约占10%),年过剩量与低利用率导致其市场价格(0.24-0.6 US kg^(-1))较低.甘油是具有三个活性羟基的多元醇,被认为是生产高价值产品的理想原料.甲酸作为甘油转化最重要的产品之一,广泛应用于农药、皮革、染料和医药行业,将甘油电氧化(EGOR)为甲酸(FA)不仅能有效避免资源过剩造成浪费,而且能满足未来对甲酸燃料电池的需求.然而甘油电催化氧化途径较为复杂,涉及反应中间产物的脱氢、吸附/解吸和C-C键裂解.本文将密度泛函理论(DFT)与实验相结合,研究了在精细构建的NiCo_(2)O_(4)纳米片上通过EGOR生产FA的反应机制.DFT计算结果表明,活性羟基(OH^(*))物种可以改变EGOR生产FA过程的决速步骤(RDS),通过调节吸附中间体的吸附能可获得理想的FA产率.其中,高度羟基化的NiCo_(2)O_(4)纳米片(311)-OH^(*)晶面上具有最低的吉布斯自由能,能显著提升反应过程动力学.在理论分析的基础上,通过简易的电沉积方法精准制备了超薄NiCo_(2)O_(4)纳米片(~1.7 nm),并采用X射线吸收精细结构谱和高分辨透射电镜对催化剂进行了结构分析.结果表明,NiCo_(2)O_(4)纳米片中四面体(A_(Td))和八面体(B_(Oh))配位具有内角共享的A_(Td)-O-B_(Oh)和边共享的B_(Oh)-O-B_(Oh)构型,金属间的协同作用有效改善了材料的电子效应,有利于提供更多的吸附位点并促进EGOR过程中的电荷转移.NiCo_(2)O_(4)纳米片在EGOR中的电荷转移电阻仅为0.94Ω,电化学活性表面积高达10.25 cm^(2).相比较电催化析氧反应,NiCo_(2)O_(4)纳米片表现出了较好的EGOR性能,在10 mA cm^(-2)的电流密度下阳极功耗降低了320 mV,在100 mA cm^(-2)的电流密度时的阳极电势仅为1.46 VRHE.此外,在120 h的稳定性测试中,甘油的转化率和FA的选择性可分别保持在89%和70%.多电位步骤实验、原位电化学阻抗谱和电子顺磁共振谱结果表明,NiCo_(2)O_(4)纳米片上原�
Electrocatalytic refinery of low-value biomass-based glycerol into value-added chemicals formic acid(FA)is an attractive alternative to traditional thermochemical refineries.However,constructing non-precious catalysts with abundant active hydroxyl(OH^(*))is the main obstacle to the electrocatalytic glycerol oxidation reaction(EGOR).Herein,we combine density functional theory(DFT)and experiments to investigate EGOR over the finely constructed NiCo_(2)O_(4)nanosheets.DFT results firstly indicate that the NiCo_(2)O_(4)nanosheets exhibit the highly hydroxylated(311)-OH^(*) surface with the lowest Gibbs free energy,which significantly improves the electrochemical reaction kinetics and can achieve desirable FA yield by adjusting the adsorption energy of the adsorption intermediate.Following the theoretical prediction,ultrathin NiCo_(2)O_(4)nanosheets(~1.70 nm)are fabricated by a facile electrodeposition method with sufficient OH*on the surface.The charge-transfer resistance of NiCo_(2)O_(4)nanosheets in EGOR is only 0.94Ωand the anode power consumption can be reduced by up to 320 mV at 10 mA cm^(-2),keeping the high glycerol conversion(89%)and FA selectivity(70%)during the 120-h stability test.DFT calculations and experimental tools(e.g.,multi-potential step experiments,operational electrochemical impedance spectroscopy)confirm that OH^(*) in-situ generated on the thin nanosheets structure is essential in facilitating charge transfer between catalysts and adsorbed molecules to enhance C–C bond cleavage.This work offers a guideline for the rational design of robust catalysts for the selective upgrading of biomass-derived chemicals.
作者
段妍
薛米风
刘彬
张曼
王宇辰
王宝俊
章日光
严凯
Yan Duan;Mifeng Xue;Bin Liu;Man Zhang;Yuchen Wang;Baojun Wang;Riguang Zhang;Kai Yan(Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology,School of Environmental Science and Engineering,Sun Yat‐sen University,Guangzhou 510275,Guangdong,China;State Key Laboratory of Clean and Efficient Coal Utilization,College of Chemical Engineering and Technology,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;School of Environmental Science and Engineering,Guangdong University of Technology,Guangzhou 510006,Guangdong,China)
基金
国家重点研发计划(2023YFC3905804)
广州市科技计划项目(202206010145)
国家自然科学基金项目(22078374,22378434)
广东省科技计划项目(2021B1212040008)
广东省岭南现代农业重点实验室项目(NT2021010).
