非贵金属催化剂在羟甲基糠醛电氧化增值中的应用 高等学校化学学报    2023, 44 (5): 20220710-.   DOI:10.7503/cjcu20220710

Fig.5 Sum Frequency Generation(SFG) spectra recorded at the working electrode/electrolyte interface after running the cell at various voltages for 90 min(A) and by monitoring the reaction at different times at 1.45 V(vs. RHE) in 1 mol/L KOH and 20 mmol/L HMF(B)^[51]
Copyright 2019， Wiley-VCH GmbH.

正文中引用本图/表的段落

值得注意的是， 目前HMFOR路径与催化剂的关系尚不明确. 大部分过渡金属Xide催化剂表面HMFOR沿着HMF→HMFCA→FFCA→FDCA的路径进行， 例如Ni₃S₂/NF催化剂［49］、 Ni₂P/NF催化剂［50］、 Ni₃N@C催化剂［51］及Ni _x B催化剂［52］等， 但也存在特例. Sun等［47］发现， 同样是磷化物， CoP/NF催化剂主要沿着HMF→DFF→FFCA→FDCA的路径进行， 其法拉第效率接近100%， FDCA转化率高于90%［47］. 目前对于这一问题还没有明确的认识. 我们推测HMFOR路径的不一致可能是由于不同催化剂组分造成的， 即CoP对DFF的电催化氧化活性远高于对HMFCA的电催化氧化活性， 而Ni₂P则相反. 当然， 这一推测尚未被证实. 因此， 发展先进表征手段对于HMFOR机理和非贵金属催化剂构效关系的深入理解十分必要. 例如电化学原位和频振荡光谱可被用于研究Ni₃N催化剂表面的HMFOR机理［51］. 由图5可见， 在电极电势为1.05~1.25 V时， 只能检测到HMF的信号， 这意味着HMFOR尚未发生； 随着电势增加到1.35 V， 和频振荡光谱在1335和1380 cm-1处出现了新峰， 对应于HMFCA的生成； 进一步增加电势到1.45 V， 光谱上开始出现FFCA和FDCA的特征峰； 电极电势继续增加到1.70 V时， 只能检测到FDCA的信号峰， 说明该反应的终产物是FDCA. 上述实验结果与HPLC结合可以证明HMF→HMFCA→FFCA→FDCA路径.

本文的其它图/表

• Fig.1  Schematic illustration of HMF and its possible oxidation products
• Table 1  The value-added products derived from HMFOR and their possible applications
• Fig.2  TEM image of Pd₁Au₂/C catalyst(A) and product distribution on Pd₁Au₂/C for the oxidation of 0.02 mol/L HMF in 0.1 mol/L KOH(B)^[28]Copyright 2014， the Royal Society of Chemistry.
• Fig.3  Schematic of the electrochemical cells with Co⁃P/CF catalyzed HMF oxidation(A), concentrations of HMF and oxidation products over passed charge during the chronoamperometry experiment conducted at 1.423 V in 1.0 mol/L KOH containing 50 mmol/L HMF(B)^[47], conversion and yield(%) changes of HMF and its oxidation products during the electrochemical oxidation of HMF at 1.54 V in a 0.5 mol/L borate buffer solution containing 5 mmol/L HMF and 7.5 mmol/L TEMPO(C)^[48]（A， B） Copyright 2016， American Chemical Society； （C） Copyright 2015， Nature Publishing Group.
• Table 2  Typical non-precious metal catalysts and their HMFOR performances
• Table 3  The oretical ΔH_f^FERE and experimental ΔH_f^exp of several typical transition metal-based compounds^[60]
• Fig.4  Morphological features of Ni₂P NPA/NF and conversation of FDCA^[50]（A） XRD pattern of Ni₂P NPA/NF with the corresponding standard patterns of Ni₂P and Ni； （B， C） SEM images of Ni₂P NPA/NF with different magnifications； （D） SEM and the corresponding elemental mapping images of Ni₂P NPA/NF； （E） LSV curves of Ni₂P NPA/NF at a scan rate of 2 mV/s in 1.0 mol/L KOH with and without 10 mmol/L HMF； （F） conversion and yield（%） changes of HMF and its oxidation products during the electrochemical oxidation of HMF at 1.423 V（vs. RHE） in 1.0 mol/L KOH with 10 mmol/L HMF； （G） faradaic efficiencies of Ni₂P NPA/NF for FDCA production under three successive electrolysis cycles.Copyright 2016， Wiley-VCH GmbH.
• Table 4  Typical transition metal Xides and their derivates(real active materials) during anodic reactions
• Fig.6  Physical characterizations of the reconstructed Ni(OH)₂/NiFeP after potentiostatic HMFOR polarization
• Fig.7  Theoretical calculation results to unravel the underlying HMFOR mechanisms on CuO⁃PdO catalyst^[83]（A） Adsorption configuration of the HMF and OH on CuO（111） surface and the as-designed CuO-PdO； （B） HMF and OH adsorption free energy； （C） free energy diagram and adsorption configurations of HMFOR intermediates on CuO（111） and CuO⁃PdO； （D） promoting mechanism of the HMFOR； （E） the charge density difference of PdO on CuO（111） surface.Copyright 2022， Wiley-VCH GmbH.
• Fig.8  Electrochemical HMFOR performance using NiFe⁃LDHs catalyst^[57]（A） HPLC chromatogram traces of the various products at different reaction times following an HMF electrochemical oxidation reaction； （B） digital photograph showing the color change of the anodic electrolyte during the electrochemical HMF oxidation process； （C） concentration changes of HMF and its oxidation products with the time of chronoamperometric tests at 1.33 V vs. RHE； （D） HMF concentration changes during four successive cycles.Copyright 2018， American Chemical Society.