Supplementary Material
IrOx/CNxNTs as electrocatalysts for oxygen evolution reaction in a HCO3−/CO2 system at neutral pH
WeixinLv1, Suxian Liu1, Rui Zhang 1, *, WenjuanWang1, Zhongxia Wang1, Lei Wang2, Wei Wang1, *
1School of Chemistry and Chemical Engineering,Yancheng Institute of Technology, Yancheng 224051, China
2Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education of the People’s Republic of China, Heilongjiang University, Harbin 150080, China
*Corresponding author. +86 515 88298848 (R. Zhang).
E-mail address: (R. Zhang); (W. Wang).
Analysis
The X-ray diffraction (XRD) measurement was carried out with a BlukerRigaku D/MAX 2200 diffractometer using Cu Kα radiation (λ = 1.54056 Å). The Raman spectra were recorded at ambient temperature on an LabRAM HR800 Raman spectrometer. The contents of Ir in IrOx/CNxNTs catalysts were measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES, recorded on Perkin Elmer Optima-4300DV). Before the ICP-AES measurement, each sample should be dissolved into aqua regia, and then the solution was transferred to an autoclave for solvothermal reaction at 150 °C for 8 h. This method can be used to ensure the metal Irbeing corroded.
Fig. S1 Measured masses of CNxNTs and IrOx/CNxNTs
Table S1Content of IrinIrOx/CNxNTs determined by ICP-AES.
Sample / Content of Ir (mg/g)8-Ir/C / 78.5
15-Ir/C / 133
25-Ir/C / 234
35-Ir/C / 293
After the IrOx/CNxNTs catalysts were synthesized, their weights were measured, which are shown in Fig. S1. It can be seen that the weights of all the prepared IrOx/CNxNTs catalysts are heavier than that of CNxNTs (30 mg), and the weight of the IrOx/CNxNTs increases with the iridium content. It should be noted that a small amount of samples was lost during the washing process. Except for this system factor, the above result can prove that Ir is effectively loaded onto the surface of the CNxNTs for IrOx/CNxNTs catalysts. The contents of Ir inIrOx/CNxNTs catalysts were also determined by ICP-AES, and the results are shown in Table S1. The mass concentrations of Ir determined by ICP-AES are 7.85%, 13.3%, 23.4% and 29.3%, which are calculated by the equation:
(1)
and are a little lower than the theoretical values 8%, 15%, 25% and 35% (calculated by the equation 2).
(2)
If the mass of oxygen in IrOx/CNxNTs is taken into account in the calculation, the theoretical value of the mass concentration of Ir will closer to the mass concentration of Ir determined by ICP-AES.
Fig. S2 XRD patterns of CNxNTs and IrOx/CNxNTs
The XRD patterns of CNxNTs and IrOx/CNxNTs are shown in Fig. S2. It can be observed that the diffraction peaks at 26.1 and 43° for all the samples can be attributed to (002) and (100) planes of graphite, respectively [1]. The difference between the IrOx/CNxNTs and the CNxNTs is that the peak intensity of the IrOx/CNxNTs decreases with the increase of the IrOx loading. This result is also indicated that IrOx nanoparticles are covered on the surface of the CNxNTs. No obviously diffraction peaks ofIrOx nanoparticles can be observed. This is due to the low crystallinity of the IrOx nanoparticles.
Fig. S3Ramanspectra of CNxNTs and IrOx/CNxNTs
The Raman spectra of CNxNTs and IrOx/CNxNTs are shown in Fig. S3. All spectra show two resonance peaks at around 1361 and 1585 cm-1, which correspond to the sp3 graphitic configuration (D-band) and the sp2 graphitic configuration (G-band) of CNxNTs [2]. No obviously diffraction peaks of IrOx nanoparticles can be observed.
References:
[1]Yue B, Ma Y, Tao H et al (2008) CNx nanotubes as catalyst support to immobilize platinum nanoparticles for methanol oxidation, J. Mater. Chem. 18:1747-1750.
[2]Zhang Y, Huang B, Ye J, Ye J (2017) A sensitive and selective amperometric hydrazine sensor based on palladium nanoparticles loaded on cobalt-wrapped nitrogen-doped carbon nanotubes, J. Electroanal. Chem. 801:215-223.
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