N2-Plasma-Induced CN-Vacancies in NiCoFe PBAs Enhance Selective Oxygen Evolution Electrocatalytic Performance in Alkaline Seawater

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Abstract
Cheap and advanced electrocatalysts for the oxygen evolution reaction (OER) are vitally significant but challenging for seawater electrolysis. Herein, a glow discharge N2 plasma is used to etch the [Fe(CN)6]4- group of the NiCoFe Prussian blue analogue (PBA) framework by highly reactive nitrogen radicals (the catalyst named N2-NiCoFe-PBA). Abundant CN vacancies (VCN) generated by this etching effectively suppress the Fe loss from N2-NiCoFe-PBA, while the lack of VCN results in the Fe leaching from the NiCoFe-PBA precursor during the anodic process. Consequently, N2-NiCoFe-PBA and NiCoFe-PBA are transformed into real active phases of NiCoFeOOH and NiCoOOH during the OER process, respectively. Theoretical calculations display that NiCoFeOOH has superior adsorption capacity toward OH- over Cl- to NiCoOOH, which is beneficial to excellent OER activity and anticorrosion performance in alkaline seawaters. In alkaline simulated and natural seawater, N2-NiCoFe-PBA exhibits much better OER performance with smaller η100 (293 and 323 mV) than NiCoFe-PBA (405 and 434 mV). N2-NiCoFe-PBA can run stably over 110 h in an alkaline high-salty electrolyte (1 M KOH + 2.0 M NaCl) at 250 mA cm-2. This study provides a modification method without destroying the structure to develop efficient and stable OER catalysts for seawater electrolysis.
Funding Information
  • Natural Science Foundation of Shandong Province (ZR2014JL013, ZR2019MB062, ZR2024MB130)
  • Science Fund for Distinguished Young Scholars of Shandong Province (2023HWYQ-091)
  • Key Technology Research and Development Program of Shandong Province (2017GGX20143)
  • Qingdao New Energy Shandong Laboratory (QNESL OP202305)

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