The selection of elements, tune of compounds types and modification of structure are important ways to improve OER activity of high-entropy alloys. The reconstruction behavior of film electrodes during OER process revealed that Mo element has a strong promoting effect on the reconstruction of FeCoNi-based films. It is shown by first-principles that electron-deficient region could be formed near Mo, and electron-rich region could be formed near surrounding elements of Mo. Charge transfer may be the reason that Mo promotes reconstruction of high-entropy alloys. Compared with FeCoNiCr film electrode, FeCoNiCrMo film electrode, the 2p 3/2 binding energy peaks of Fe/Co/Ni in which are shifted forward, has more oxygen-containing species and oxygen vacancies. The study also revealed the existence of lattice oxygen mechanism during OER process. The deposition thickness of alloy film has a linear relationship with sputtering time and deposition rate of FeCoNiCrMo. There is an optimal deposition thickness of FeCoNiCrMo film electrode for OER. FeCoNiCrMo film electrodes have the most excellent OER performance: the overpotential is 268 mV, and the Tafel slope is 57.6 mVdec −1 .
Peng Feng,Donghai Xu,Gang Yin,Kunkun Song,Ruibo Wang,Zhiyuan Li,Pan Wang
This study investigated the corrosion behavior of 316 L (316LSS) and 304 (304SS) stainless steels under a Na 2 SO 4 deposition layer in supercritical water (SCW). The salt layer reduced oxide film densification versus pure SCW, with 304SS exhibiting more severe corrosion (e.g., pitting) due to the absence of Mo which resists pitting corrosion. Without the salt layer, oxide film thicknesses were 6.50 µm (316LSS) and 1.60 µm (304SS); in contrast, 6.52 µm and 9.33 µm, respectively, indicating thicker in SCW with the salt layer. At 723 K and 25 MPa, higher water density increased Ni/Fe ion solubilities, while the salt layer trapped these ions in the microenvironment between the layer and oxide film, generating a locally acidic and oxidizing environment via hydrolysis of Ni/Fe ions. This process accelerated metal ion leaching and oxide dissolution, further enhanced in the presence of SO 4 2- . Na 2 SO 4 deposition layer and SCW synergistically intensified corrosion in both alloys.
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