Denitrification in bioretention systems based on corncob biochar produced at low pyrolysis temperature: The efficacy and the mechanisms

Spinel‐Structured High‐Entropy Oxide Nanofibers as Electrocatalysts for Oxygen Evolution in Alkaline Solution: Effect of Metal Combination and Calcination Temperature

“…Instead, the increased octahedral occupation by Co 2+ and Ni 2+ cations (and/or the increased Ni 2+ :Co 2+ ratio) might be responsible for the 𝜂 OER lowering observed moving from CoNi-600 to CoNi-900. In the case of Zncontaining HESOs, the decrease of T C favors the occupation of 16d sites by Zn 2+ cations at expense of the occupation by the most redox-active [24,32,86,90] Co 2+ /Co 3+ and Ni 2+ /Ni 3+ species in CoZn and NiZn NFs, respectively (Figure 8b,c). This reflects in the progressive worsening in the catalytic activity (𝜂 OER increase) observed in CoZn and NiZn NFs with increasing T C (Figure 10b).…”

“…The changes in the occupation of octahedral sites induced by the variation of T C represent another aspect related to the cation distribution that also has a great influence on the electrocatalytic behavior of the HESO fibers. In the case of CoNi NFs, incomplete attainment of the ECD (Figure 8a) corresponds to higher occupation of 16d sites by highly active [24,27,32,86,90] Co 2+ and Co 3+ cations. The same consideration would apply to Ni 2+ and Ni 3+ cations if the distribution of cations proposed by Sarkar et al [83] Figure 10.…”

“…As mentioned above, defect engineering has recently emerged as a viable strategy to improve the electrocatalytic performance of nanomaterials. [21,[30][31][32][33][34][35] Among the various type of defects, point defects and in particular vacancy defects are the most exploited in OER. [21] Cationic vacancies require higher formation energy compared to anionic vacancies.…”

“…[31] Greater stability (60 h) and faster kinetics (Tafel slope: 50.3 mV dec −1 ) have been reported for nanoporous spineltype high-entropy (Cr,Mn,Fe,Co,Ni) oxide with high GB density, obtained by low temperature solution combustion. [32] This work focuses on the preparation of OV-rich spinel-type electrospun HESO NFs to be used as electrocatalysts for OER in alkaline medium. The rationale is to improve their electrochemical properties through the increase of the OV-concentration and the occupation of octahedral sites by redox-active cations, while simultaneously mitigating the environmental impact of their production process.…”

“…[29] Actually, defect engineering has recently emerged as a viable strategy to improve the electrocatalytic performance of nanomaterials. [21,[30][31][32][33][34][35] Defective high-entropy rock-salt (Mg,Co,Ni,Cu,Zn) oxide prepared by electrospinning, Arannealing and air-calcination at 1000°C exhibits high stability (25 h) and lower Tafel slope (61.4 mV dec −1 ) than common low-entropy nickel and cobalt oxide (NiO and CoO) catalysts. [31] Greater stability (60 h) and faster kinetics (Tafel slope: 50.3 mV dec −1 ) have been reported for nanoporous spineltype high-entropy (Cr,Mn,Fe,Co,Ni) oxide with high GB density, obtained by low temperature solution combustion.…”