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Article

Cobalt-Doped Iron Phosphate Crystal on Stainless Steel Mesh for Corrosion-Resistant Oxygen Evolution Catalyst

by
Jaun An
1,
Hyebin Choi
1,
Keunyoung Lee
2 and
Ki-Young Kwon
1,2,*
1
Department of Chemistry and RIGET, Gyeongsang National University, Jinju 52828, Republic of Korea
2
HAP Materials, 352-407, 501, Jinju-daero, Jinju 52828, Republic of Korea
*
Author to whom correspondence should be addressed.
Catalysts 2022, 12(12), 1521; https://doi.org/10.3390/catal12121521
Submission received: 1 November 2022 / Revised: 23 November 2022 / Accepted: 24 November 2022 / Published: 25 November 2022
(This article belongs to the Special Issue Novel Photo(electro)catalysts for Energy and Environmental Applications)
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Abstract

:
We report an oxygen evolution reaction (OER) catalyst prepared by the incorporation of cobalt-doped iron phosphate on stainless steel mesh (SSM) through a one-step hydrothermal method. Compared to the catalytic property of bare SSM, our OER catalyst (0.84-CoFePi) showed a 42% improvement in current density at the potential of 1.9 V vs. RHE, and the onset potential was decreased by 26.5 mV. Furthermore, the loss in current density of bulk electrolysis after 12 h in 1 M KOH (pH 14) solution and 0.0441 wt% H2SO4 (pH ≈ 3) containing 0.1 M NaCl solution was negligible (3.1% and 3.2%, respectively). Moreover, our cobalt-doped iron phosphate on SSM exhibits the dramatic improvement in corrosion resistance to a basic, mild acidic solution and chloride ions compared to bare SSM.

1. Introduction

Replacing fossil fuels with renewable energy can limit accelerating global warming and cater to the rapid increase in energy demand [1]. Hydrogen fuel, currently being one of the most attractive alternatives to fossil fuels, has the highest gravimetric energy density, and the only combustion byproduct of hydrogen is water [2,3,4,5,6]. Hydrogen can be generated by photochemical [7,8], thermochemical [9,10], and electrochemical water decomposition [11,12,13,14]. Among them, electrochemical water splitting is currently a convenient and practical method for the generation of hydrogen with high purity. Water electrolysis is accomplished with two half-reactions, those are oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Particularly, OER, involving hydrogen coupled four electron transfer is the rate-determining step of water electrolysis [15,16,17]. Therefore, the development of OER catalyst is intensively studied to overcome the sluggish kinetics of OER [18,19,20,21,22,23,24,25]. Stainless steel (SS) is inexpensive, conductive, and stable in basic as well as mild acidic solution [26,27]. Therefore, there has been lots of effort to apply SS as an anode material for water electrolysis [28,29,30]. Additionally, stainless steel mesh (SSM) has a larger surface area due to its porous structure in which fibers are woven in a grid [31,32]. However, the impact of corrosion on SSM needs to be considered in the presence of acidic fluids or chloride solution [33,34,35,36]. Therefore, attention has been focused on improving the corrosion resistance of stainless steel.
Generally, transition metal phosphates have high catalytic performance [37,38], and doping transition metals such as Co, Fe can improve the OER activity by dropping overpotential and delivering high current density [39,40,41]. Particularly, amorphous cobalt phosphate was reported to have excellent OER properties by the Nocera group [42,43,44,45,46,47,48]. Here, we fabricated an OER catalyst in which the cobalt-doped iron phosphate is incorporated on SSM. To the best of our knowledge, it is the first report of fabricating an OER catalyst through one-step hydrothermal reaction by simply immersing SSM into the aqueous solution of phosphoric acid and cobalt nitrate. During the formation of our OER catalyst, SSM is slightly corroded by phosphoric acid, allowing iron to leach from SSM into the solution, then the insoluble salt of cobalt-doped iron phosphate precipitates on the surface of SSM. Due to the importance of leached iron concentration, we optimized the concentration of phosphoric acid for the preparation of the OER catalyst. Compared to the catalytic property of bare SSM, our OER catalyst (0.84-CoFePi) showed a 42% improvement in current density at the potential of 1.9 V vs. RHE, and the onset potential decreased by 26.5 mV (266.2 mV to 239.7 mV). Furthermore, the loss in current density after 12 h of bulk electrolysis under 0.0441 wt% H2SO4 containing 0.1 M NaCl solution was less than 3.2%. Moreover, our cobalt doped iron phosphate on SSM exhibits improvement in corrosion resistance to basic, mild acidic and chloride ions containing solutions compared to bare SSM.

2. Results

The SEM images of bare SSM and prepared SSMs are shown in Figure 1a–l. Figure 1a shows the SEM image of a bare SSM in which stainless steel fibers with smooth surface are woven in a grid. SSMs were corroded by hydrothermal reaction in aqueous phosphoric acid solution. Additionally, increment in acid concentration accelerated the corrosion of SSM, making the smooth surface rougher (Figure 1b–d). The corrosion resulted in reduction in fiber thickness of SSM. The measured fiber thickness of SSMs were 24.67 μm (bare SSM), 23.65 μm (SSM-0.84), 22.82 μm (SSM-2.50), and 6.63 μm (SSM-4.14) as shown in Figure 1a–d. Compared to bare SSM, the fiber thickness of SSM-0.84 and SSM-2.50 was reduced by 1.02 and 1.85 μm, respectively, by the slight corrosion (Figure 1b,c). On the other hand, SSM-4.14 shows dramatic reduction of 18.04 μm (24.67 μm to 6.63 μm) in fiber thickness (Figure 1d,m). SSM was sometimes completely dissolved by drastic corrosion in 4.14 wt% H3PO4 solution. Figure S1 is a picture of SSM that corroded away after the hydrothermal reaction in 4.14 wt% H3PO4 solution, except for the part inserted into as homemade Teflon holder. Furthermore, in 8.14 wt% H3PO4 solution, SSM was totally melted after hydrothermal reaction. Figure 1e–l are SEM images of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, and 8.14-CoFePi. In hydrothermal reaction, the addition of cobalt nitrate to phosphoric acid aqueous solution resulted in two crucial changes on SSM. First, octahedral crystals were precipitated. Second, the corrosion of SSM was obviously reduced compared with cobalt-free SSMs. For instance, SSM-4.14 and 4.14-CoFePi were prepared under the same acid concentration. However, as shown in Figure 1d,k, the fiber thickness of SSM-4.14 (6.63 μm) is much thinner than that of 4.14-CoFePi (23.22 μm). Therefore, it is evident that cobalt nitrate inhibited the corrosion of SSM. Figure 1n is a bar graph comparing the average vertical diagonal lengths of crystals measured from the SEM image. The average crystal sizes of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, and 8.14-CoFePi were 30.29 μm, 31.56 μm, 39.89 μm, and 56.19 μm, respectively, confirming that the larger crystals were synthesized at higher acid concentration.
XRD patterns of all prepared OER catalysts on SSMs including bare SSM are represented in Figure 2a. Three peaks marked with stars are from bare SSM. All XRD patterns of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, and 8.14-CoFePi are identical, indicating that the same substance has been synthesized regardless of the acid concentration. The crystals synthesized on SSM are confirmed to be Fe2.80(PO4)1.98O0.26(OH)1.82, iron phosphate oxide hydroxide (JCPDS No. 01-070-5891). Our crystal shape and XRD pattern matched well with the iron phosphate reported by Quanyi Zhou et al. [49]. The IR spectra of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, 8.14-CoFePi including bare SSM are shown in Figure 2b. The IR spectra of all the prepared SSMs were very similar. The peak at 746 cm−1 belongs to the stretching of P-O-P linkages [50]. Peaks at 949 cm−1 and 1027 cm−1 are committed to the symmetric and asymmetric stretching peaks of P-O bond, respectively [39]. Additionally, the peak from Fe-O stretching and vibration mode appeared at 567 cm−1 and 480 cm−1, respectively [51]. It was confirmed by IR spectrum that the crystals synthesized by hydrothermal reaction were composed of Fe, P, and O bonds. Therefore, both XRD and FT-IR revealed that the synthesized crystal is iron phosphate oxide hydroxide. On the other hand, the XRD pattern from cobalt species (cobalt oxide or cobalt phosphate) does not appear.
EDS analysis was performed to investigate the element distribution of the prepared SSM. In Figure 3b–d, it was confirmed that P, O, and Co were more abundant in the crystal than the SSM substrate, indicating that the crystal is composed of phosphate anions and cobalt cations. On the other hand, Fe, Cr, and Ni are distributed more in the SSM substrate than the crystal (Figure 3e–g). Considering that the 316 SSM used in this experiment is known to be mainly composed of Fe, Cr, and Ni, it can be easily expected that the Fe, Cr, Ni will be more abundant in the substrate than the crystal.
XPS analysis was performed to investigate the surface composition of 0.84-CoFePi (Figure 4). The XPS survey spectrum indicates the presence of Co, Fe, P and O (Figure 4a). Additionally, the atomic percentages of Co, Fe, P and O were 6.97%, 7.69%, 14.35%, and 69.12%, respectively. Figure 4b shows the XPS spectrum in Co 2p region, and the binding energy (BE) at 781.43 eV and 797.15 eV are assigned to be Co 2p3/2 and Co 2p1/2, respectively [52,53]. From the deconvolution of Co 2p spectrum, peaks at the BEs of 782.71 eV and 798.74 eV are assigned to Co2+, while the peaks at 780.52 eV and 796.56 eV are attributed to Co3+ [54,55,56,57]. Furthermore, the calculated atomic ratio of the detected Co element suggests that the Co2+ and Co3+ states exist in a ratio of 6:5. In the XPS spectrum of Fe 2p region (Figure 4c), the BEs at 711.92 eV and 725.45 eV are corresponding to the peaks of Fe 2p3/2 and Fe 2p1/2, respectively [58,59]. In addition, the deconvoluted peaks of Fe 2p at the BEs of 711.15 eV and 725.16 eV are associated with Fe2+, while the peaks at 713.71 eV and 728.18 eV are from Fe3+ [60,61,62,63]. Moreover, the atomic ratio of Fe2+/Fe3+ is 7:4. The peak in the XPS spectrum of O 1s and P 2p (Figure 4d,e) was observed with the BEs of 530.77 eV and 132.84 eV, respectively [64,65,66,67]. Therefore, from the results of XRD, FT-IR, EDS, and XPS we concluded that the crystallite is mainly composed of randomly incorporated cobalt ions on iron phosphate oxide hydroxide.
The evaluation in OER activity of all prepared catalysts is shown in Figure 5a–c. Polarization curves of prepared OER catalysts and bare SSM were recorded at the potential window from 1.0 V to 1.924 V vs. RHE, with the scan rate of 10 mVs−1 (Figure 5a). The current density at the maximum potential applied in LSV, 0.84-CoFePi showed the highest value which was increased by 42% (203.6 to 289.1 mAcm−2) compared to the bare SSM. The overpotentials of all catalysts required to drive OER at 10 mAcm−2 were lower than bare SSM (Figure 5b). Typically, 0.84-CoFePi had the lowest overpotential of 300.3 mV, which was decreased by 31.2 mV from bare SSM (331.5 mV). The OER activity of 0.84-CoFePi was compared with recently reported Co or/and Fe based catalysts in Table S1 in Supplementary Materials. In lower acid concentration, smaller crystals precipitate on SSM, which is expected to have higher OER activities due to the larger surface area [68,69,70,71,72]. To evaluate the stability of the products, bulk electrolysis was carried out (Figure 5c). The average current density was 40.2 mAcm−2 (bare SSM), 67.8 mAcm−2 (0.84-CoFePi), 42.0 mAcm−2 (2.50-CoFePi), 38.5 mAcm−2 (4.14-CoFePi), and 26.2 mAcm−2 (8.14-CoFePi). Compared to bare SSM, 8.14-CoFePi showed very poor OER activity, which was decreased in current density by 34.8%. However, 0.84-CoFePi showed drastic increase by 68.8% in current density. Furthermore, the loss in current density after 12 h of bulk electrolysis in 1 M KOH (pH 14) was 3.1% with better sustainability than bare SSM (11.8%).
It is well known that the chloride ions and low pH condition accelerate corrosion of stainless steel. Li et al. reported the corrosion behavior of stainless steel by electrochemical method performed in an aqueous solution of sulfuric acid (pH 2) with different NaCl concentration. Their results suggested that chloride ions degraded the passive film of stainless steel [73]. We accomplished the bulk electrolysis of bare SSM and 0.84-CoFePi to test the stability to H2SO4 solution (pH ≈ 3) and 0.1 M chloride ion (Figure 6b). Bare SSM was detached from sample holder due to the corrosion after 90 min of electrolysis, causing the drop in current density to zero. On the other hand, 0.84-CoFePi showed stable current density for 12 h. The loss in current density of 0.84-CoFePi after 12 h of bulk electrolysis was less than 3.2%. SEM analysis was accomplished to verify the surface morphology of bare SSM and 0.84-CoFePi (Figure 6b,c) after the bulk electrolysis. The small holes (insert of Figure 6b) appeared in bare SSM even after short OER time of 90 min, indicating that severe corrosion occurred. On the other hand, the mesh surface of 0.84-CoFePi was clean after 12 h of OER with no trace of corrosion. Therefore, our catalyst had improved durability in acidic solution compared to bare SSM. This result was predicted from the result of SEM previously discussed in Figure 1 in which the presence of cobalt species dramatically inhibits corrosion of SSM.

3. Materials and Methods

3.1. Materials

Phosphoric acid (85%), sulfuric acid, cobalt nitrate hexahydrate, and acetone (99.5%) were purchased from Daejung chemicals (Siheung, Republic of Korea). Sodium chloride was purchased from Sigma Aldrich (St. Louis. MO, USA). 316 Stainless steel mesh was purchased from All for lab (Seoul, Republic of Korea). Silicon glue (3145 RTV) was purchased from Dow corning. All chemicals were used as received without purification.

3.2. Cleaning SSMs and the Corrosion of SSM by Phosphoric Acid in Hydrothermal Treatment

Firstly, SSMs were cut into pieces (1 cm × 2 cm) and washed with hexane, acetone, and DI water under ultrasonication for 5 min, respectively. Then, SSMs were dried in 75 °C oven at ambient atmosphere and cooled naturally to room temperature. The 0.84, 2.50, 4.14 and 8.14 wt% phosphoric acid solutions were prepared by diluting 85% phosphoric acid with DI water. The cleaned SSM was vertically placed on a homemade Teflon holder and was immersed into the above prepared 20 mL of phosphoric acid solution in 50 mL Teflon lined autoclave, followed by heating in an oven at 200 °C for 12 h (denoted as SSM-0.84, SSM-2.50, SSM-4.14, and SSM-8.14, respectively). The autoclave was cooled down to room temperature, and the SSM was gently washed with 100 mL of DI water 3 times, and dried in 75 °C oven.

3.3. Preparation of OER Catalyst on SSMs

In this process, 0.4 mmol of cobalt nitrate hexahydrate was added to the 20 mL of 0.84, 2.50, 4.14 and 8.14 wt% H3PO4 aqueous solutions, respectively. The cleaned SSM was vertically immersed into the above prepared 20 mL of phosphoric acid and cobalt nitrate solutions in 50 mL Teflon lined autoclave, followed by heating in an oven at 200 °C for 12 h (denoted as 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, and 8.14-CoFePi, respectively). All subsequent processes were the same as done above.

3.4. Characterizations

The surface morphology and elemental analysis of hydrothermally treated SSMs were investigated by Field Emission Scanning Electron Microscope (FE-SEM, JSM-6700F, JEOL, Tokyo, Japan) with energy dispersive spectrometer (EDS). X-ray diffraction patterns (XRD) were collected from 3 kW Cu X-ray Diffractometer, (D8 Advance, Bruker AXS, Hamburg, Germany) in the 2θ range of 5–80°. Vibrational spectra of prepared SSMs were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) using Nicolet iS5 FT-IR Spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) in the wavenumber range of 400–4000 cm−1. X-ray photoelectron spectroscopy (XPS) was analyzed using NEXSA G2 (Thermo Fisher Scientific, Waltham, MA, USA).

3.5. Electrochemical Measurement

All electrochemical properties of the prepared SSMs were measured by a commercial potentiostat (Zive SP1 Wonatech, Seoul, Republic of Korea) with three-electrode system under aqueous solution of 1 M KOH (pH 14) and 0.0441 wt% H2SO4 (pH ≈ 3). In this process, 0.1 M NaCl was used as an electrolyte for the 0.0441 wt% H2SO4 solution. The prepared SSMs were applied as working electrodes, Hg/HgO (basic media) and Ag/AgCl (acidic media) for reference electrode and Pt plate as a counter electrode. The geometric area of prepared SSMs were adjusted to 1 × 1 cm2 by screening SSM using silicon sealant. All applied potentials vs. Hg/HgO and Ag/AgCl were converted into potential vs. reversible hydrogen electrode (RHE) using the following formula:
E(RHE) = E(Hg/HgO, Ag/AgCl) + 0.059 × pH (14, ≈ 3) + E0(Hg/HgO, Ag/AgCl)
Linear sweep voltammetry (LSV) was recorded at the potential range of 1.000~1.924 V vs. RHE with the scan rate of 10 mVs−1. Chronoamperometry was performed to test the sustainability of prepared SSMs for 12 h at the potential of 1.624, 2.164 V vs. RHE for basic and acidic solutions, respectively. Overpotential (η) was calculated by the following equation:
η = E(NHE) + 0.059 × pH (14, ≈ 3) − 1.23

4. Conclusions

The cobalt-doped iron phosphate on SSM was synthesized via the hydrothermal method by immersing SSM in phosphoric acid and cobalt nitrate solution. SEM images showed that the octahedral crystals were precipitated on SSM. Through the XRD, FT-IR, EDS, and XPS analysis, the octahedral crystal was confirmed to be cobalt-doped iron phosphate oxide hydroxide. Additionally, the maintained fiber thickness of SSM after hydrothermal reaction indicated that cobalt nitrate inhibited the corrosion of SSM from phosphoric acid. The improved durability of our catalyst to basic, mild acidic conditions and chloride ions is thought to be due to the amorphous cobalt oxide containing phosphate group formed on the surface of SSM, which was demonstrated by the Nocera group [42,43,44,45,46,47,48].

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal12121521/s1, Figure S1: picture of SSM that corroded away except for the part inserted into the Teflon holder. Table S1: OER activity of 0.84-CoFePi compared with recently reported Co or/and Fe based OER catalysts. References [53,74,75,76,77,78,79] are cited in the Supplementary Materials.

Author Contributions

K.-Y.K. conceived and designed the experiments; J.A. performed the syntheses of catalysts and the examination of catalytic properties; H.C. and K.L. contributed to the scientific discussion; K.-Y.K. and J.A. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2022R1I1A3071407), and by the Korea Basic Science Institute (KBSI), National Research Facilities & Equipment Center (NFEC) grant funded by the Ministry of Education (2019R1A6C1010042).

Data Availability Statement

The data are contained within the article.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The SEM images of (a) bare SSM; hydrothermally synthesized SSMs under phosphoric acid aqueous solutions (b), SSM-0.84, (c) SSM-2.50, (d) SSM-4.14; SEM images of hydrothermally synthesized SSMs under cobalt nitrate and phosphoric acid aqueous solutions (e,i) 0.84-CoFePi, (f,j) 2.50-CoFePi, (g,k) 4.14-CoFePi, and (h,l) 8.14-CoFePi; (m) Average fiber thickness of prepared SSMs and (n) Crystalline size of hydrothermally synthesized crystals on SSMs.
Figure 1. The SEM images of (a) bare SSM; hydrothermally synthesized SSMs under phosphoric acid aqueous solutions (b), SSM-0.84, (c) SSM-2.50, (d) SSM-4.14; SEM images of hydrothermally synthesized SSMs under cobalt nitrate and phosphoric acid aqueous solutions (e,i) 0.84-CoFePi, (f,j) 2.50-CoFePi, (g,k) 4.14-CoFePi, and (h,l) 8.14-CoFePi; (m) Average fiber thickness of prepared SSMs and (n) Crystalline size of hydrothermally synthesized crystals on SSMs.
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Figure 2. (a) X-ray diffraction patterns of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, 8.14-CoFePi, bare SSM and iron phosphate oxide hydroxide (JCPDS No. 01-070-5891, peaks marked with red stars represent the XRD peaks from bare SSM); and (b) FT-IR spectra of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, 8.14-CoFePi and bare SSM.
Figure 2. (a) X-ray diffraction patterns of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, 8.14-CoFePi, bare SSM and iron phosphate oxide hydroxide (JCPDS No. 01-070-5891, peaks marked with red stars represent the XRD peaks from bare SSM); and (b) FT-IR spectra of 0.84-CoFePi, 2.50-CoFePi, 4.14-CoFePi, 8.14-CoFePi and bare SSM.
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Figure 3. SEM image of (a) 0.84-CoFePi, and EDS elements mapping of 0.84-CoFePi (b) P, (c) O, (d) Co, (e) Fe, (f) Cr, and (g) Ni.
Figure 3. SEM image of (a) 0.84-CoFePi, and EDS elements mapping of 0.84-CoFePi (b) P, (c) O, (d) Co, (e) Fe, (f) Cr, and (g) Ni.
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Figure 4. (a) XPS survey spectrum for iron phosphate oxide hydroxide crystal. XPS spectra of iron phosphate oxide hydroxide crystal in the (b) Co 2p, (c) Fe 2p, (d) O 1s, and (e) P 2p regions.
Figure 4. (a) XPS survey spectrum for iron phosphate oxide hydroxide crystal. XPS spectra of iron phosphate oxide hydroxide crystal in the (b) Co 2p, (c) Fe 2p, (d) O 1s, and (e) P 2p regions.
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Figure 5. Electrochemical (OER) analysis of all hydrothermally synthesized OER catalysts, and bare SSM: (a) LSV curves examined with the scan rate of 10 mVs−1 in 1 M KOH electrolyte, (b) The overpotentials at current density of 10 mAcm−2, and (c) Bulk electrolysis plotted from 12 h of hydrolysis at the voltage of 1.624 V vs. RHE in 1 M KOH electrolyte.
Figure 5. Electrochemical (OER) analysis of all hydrothermally synthesized OER catalysts, and bare SSM: (a) LSV curves examined with the scan rate of 10 mVs−1 in 1 M KOH electrolyte, (b) The overpotentials at current density of 10 mAcm−2, and (c) Bulk electrolysis plotted from 12 h of hydrolysis at the voltage of 1.624 V vs. RHE in 1 M KOH electrolyte.
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Figure 6. (a) Bulk electrolysis of bare SSM and 0.84-CoFePi in 0.0441 wt% H2SO4 solution containing 0.1 M NaCl at the voltage of 2.164 V vs. RHE for 12 h; SEM images of (b) bare SSM after the bulk electrolysis, and (c) 0.84-CoFePi after the bulk electrolysis.
Figure 6. (a) Bulk electrolysis of bare SSM and 0.84-CoFePi in 0.0441 wt% H2SO4 solution containing 0.1 M NaCl at the voltage of 2.164 V vs. RHE for 12 h; SEM images of (b) bare SSM after the bulk electrolysis, and (c) 0.84-CoFePi after the bulk electrolysis.
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An, J.; Choi, H.; Lee, K.; Kwon, K.-Y. Cobalt-Doped Iron Phosphate Crystal on Stainless Steel Mesh for Corrosion-Resistant Oxygen Evolution Catalyst. Catalysts 2022, 12, 1521. https://doi.org/10.3390/catal12121521

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An J, Choi H, Lee K, Kwon K-Y. Cobalt-Doped Iron Phosphate Crystal on Stainless Steel Mesh for Corrosion-Resistant Oxygen Evolution Catalyst. Catalysts. 2022; 12(12):1521. https://doi.org/10.3390/catal12121521

Chicago/Turabian Style

An, Jaun, Hyebin Choi, Keunyoung Lee, and Ki-Young Kwon. 2022. "Cobalt-Doped Iron Phosphate Crystal on Stainless Steel Mesh for Corrosion-Resistant Oxygen Evolution Catalyst" Catalysts 12, no. 12: 1521. https://doi.org/10.3390/catal12121521

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