CHEMICAL SCIENCE

Benzoate intercalation NiFe-LDH nanosheet array for efficient and stable seawater electrolysis!


On August 12, 2022, Tsinghua University hosted the high-starting energy journal Nano Research Energy (https://www.sciopen.com/journal/2790-8119Professor Sun Xuping, Associate Editor-in-Chief of the Institute of Fundamental and Frontier Research of the University of Electronic Science and Technology of China, presented a title at Nano Research Energy“Benzoate anions-intercalated NiFe-layered double hydroxide nanosheet array with enhanced stability for electrochemical seawater oxidation”The latest research results.

Hydrogen energy is an energy carrier with high energy density and environmental friendliness. As a simple, economical and eco-friendly hydrogen production technology, hydrogen production by electrolyzed water stands out in terms of growing global energy demand. Currently, many low-cost water electrolyzers are being developed. But almost all systems use freshwater as an electrolyte, which undoubtedly puts a heavy strain on freshwater resources. If the direct electrolysis of seawater to produce hydrogen, hydrogen as a fuel will produce high-purity fresh water, which will achieve the purpose of seawater purification and hydrogen production at the same time. However, the high concentration of chloride ions in seawater will not only compete with the oxygen evolution reaction of electrolyzed water at the anode, but also corrode the oxygen evolution reaction catalyst. Therefore, the development of efficient and stable oxygen evolution reaction catalysts for electrolysis of seawater to hydrogen production has become a challenging research topic.

In response to these challenges, the team of Professor Sun Xuping of the Institute of Fundamental and Frontier Research of the University of Electronic Science and Technology of China reported the recent discovery that the benzoate intercalation NiFe-LDH nanosheet array (BZ-NiFe-LDH/CC) grown on carbon cloth can be used as an efficient and stable electrocatalyst for oxygen evolution reaction. In the process of alkaline seawater oxidation, BZ-NiFe-LDH/CC can provide a large LDH layer spacing, inhibit chlorine (electro)chemical corrosion, and alleviate the local pH drop of the electrode. The BZ-NiFe-LDH/CC requires only an overpotential of 320 mV to achieve a current density of 500 mA cm-2 in 1 M KOH. In contrast to the rapid activity attenuation of NiFe-LDH/CC over long periods of electrolysis, BZ-NiFe-LDH/CC enables stable 100 hours of electrolysis in alkaline seawater at an industrial-grade current density of 500 mA·cm–2. In situ Raman spectroscopy studies further determined the structural changes of disordered δ (NiIII-O) during the oxidation of seawater.

Country 1M Schematic diagram of the oxidation strategy of NiFe-LDH in benzoate intercalation to stabilize seawater. (a) NiFe-LDH and (b) BZ-NiFe-LDH.Figure 2. (a) Polarization curves of NiFe-LDH/CC, BZ-NiFe-LDH/cc and RuO2/CC in 1 M KOH, (b) corresponding Tafir diagrams of different catalysts. (c) Polarization curve of BZ-NiFe-LDH/CC in different electrolytes. (d) Comparison of the overpotentials required for BZ-NiFe-LDH/CC to reach 100, 200 and 500 mA cm-2 in different electrolytes. (e) Comparison of the overpotential required for different seawater oxidation electrocatalysts to achieve a current density of 100 mA cm-2.

Figure 3. (a) Timing current curves of BZ-NiFe-LDH/CC and NiFe-LDH/CC at fixed potentials of 2.24 V and 2.41 V, respectively, in alkaline seawater. (b) SEM images of BZ-NiFe-LDH/CC and (c) NiFe-LDH/CC after durability testing in alkaline seawater. (d) XRD spectra of BZ-NiFe-LDH/CC and NiFe-LDH/CC after stability testing in alkaline seawater. (e) Fe and Ni concentrations and digital photographs of electrolytes after durability tests of BZ-NiFe-LDH/CC and NiFe-LDH/CC in alkaline seawater (illustrations). (f) The atomic ratio of BZ-NiFe-LDH/CC before and after the durability test of BZ-NiFe-LDH/CC in alkaline seawater before and after the Fe 2p and Ni 2p (%). (g) Comparison of the stability of BZ-NiFe-LDH/CC with other electrocatalysts for seawater oxidation reported in the literature.

Figure 4. (a) In situ Raman spectra of BZ-NiFe-LDH/CC oxidation reaction in alkaline seawater. (b) The evolution of I455/I529 and I471/I551 with potential and electronic configurations at Ni2+ and Ni3+ sites. (c) The light blue region corresponds to the v(NiII-O) phase transition of BZ-NiFe-LDH/CC from 1.2 V to 1.8 V, while the light pink region shows the δ (NiIII-O) change of BZ-NiFe-LDH/CC from 1.9 V to 2.5 V. (d) In situ Raman spectra of BZ-NiFe-LDH/CC and (e) NiFe-LDH/CC electrolyzed in alkaline seawater for 30 h at a 1.9 V potential. (f) Changes in alkaline seawater oxidation occur on the surface of the BZ-NiFe-LDH/CC electrode.

Related Paper Information:

Zhang, L. C.; Liang, J.; Yue, L. C.; Dong, K.; Li, J.; Zhao, D. L.; Li, Z. R.; Sun, S. J.; Luo, Y. S.; Liu, Q.; Cui, G. W.; Alshehri, A. A.; Guo, X. D.; Sun, X. P. Benzoate anions-intercalated NiFe-layered double hydroxide nanosheet array with enhanced stability for electrochemical seawater oxidation. Nano Res. Energy 2022, 1: e9120028. DOI: 10.26599/NRE.2022.9120028. https://doi.org/10.26599/NRE.2022.9120028

As a companion journal to Nano Research, Nano Research Energy (ISSN: 2791-0091; e-ISSN: 2790-8119; Official website: https://www.sciopen.com/journal/2790-8119Launched in March 2022, it is co-editor-in-chief of Professor Qu Liangti of Tsinghua University and Professor Chunyi Zhi of the City University of Hong Kong. Nano Research Energy is an international multidisciplinary and open access journal focusing on the cutting-edge research and application of nanomaterials and nanoscience and technology in new energy-related fields, benchmarking against top international energy journals, and is committed to publishing high-level original research and review papers. APC fees will be waived until 2023, and teachers are welcome to submit their articles. Please contact NanoResearchEnergy@tup.tsinghua.edu.cn for submissions.

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