Experimental and Theoretical Insights into the Borohydride-Based Reduction-Induced Metal Interdiffusion in Fe-Oxide@NiCo₂O₄ for Enhanced Oxygen Evolution

Abstract

The oxygen evolution reaction (OER) plays a key role in determining the performance of overall water splitting, while a core technological consideration is the development of cost-effective, efficient, and durable catalysts. Here, we demonstrate a robust reduced Fe-oxide@ NiCo 2 O 4 bilayered non-precious-metal oxide composite as a highly efficient OER catalyst in an alkaline medium. A bilayered oxide composite film with an interconnected nanoflake morphology (Fe 2 O 3 @NiCo 2 O 4 ) is reduced in an aqueous NaBH 4 solution, which results in a mosslike Fe 3 O 4 @NiCo 2 O 4 (reduced Fe-oxide@NiCo 2 O 4 ; rFNCO) nanostructured film with an enhanced electrochemical surface area. The rFNCO film demonstrates an outstanding OER activity with an extraordinary low overpotential of 189 mV at 10 mA cm −2 (246 mV at 100 mA cm −2 ) and a remarkably small Tafel slope of 32 mV dec −1 . The film also shows excellent durability for more than 50 h of continuous operation, even at 100 mA cm −2 . Furthermore, density functional theory calculations suggest that the unintentionally in situ doped Ni during the reduction reaction possibly improves the OER performance of the rFNCO catalyst shifting d-band centers of both Fe and Ni active sites. KEYWORDS: bilayered Fe 3 O 4 /NiCo 2 O 4 , chemical reduction, metal interdiffusion, electrocatalytic water splitting, oxygen evolution reaction (OER)

Experimental correlation of Mn3+cation defects and electrocatalytic activity of α-MnO2– an X-ray photoelectron spectroscopy study

“…212–219 However, herein we employed 0.0709 mF cm −2 for C s corresponding to the areal capacitance of the bare GC disk electrode, that is, the substrate electrode for the preparation of α-MnO 2 -AB thin-film WEs. 17 On the other hand, according to McCrory et al , 157 for metal oxide catalysts in NaOH and KOH solutions C s values ranging from 0.022 mF cm −2 to 0.130 mF cm −2 are reported, 220–232 thus the C s value based on the bare GC disc electrode, that was used in our work, is well within this range. However, since original (untreated) data to all double-layer capacitance measurements is provided in the ESI† to this manuscript, it will be straightforward for other groups to convert to ECSAs based on other C s values, or the specific capacitance of an atomically flat α-MnO 2 surface, which will possibly be determined in a future study, respectively.…”

“…[212][213][214][215][216][217][218][219] However, herein we employed 0.0709 mF cm À2 for C s corresponding to the areal capacitance of the bare GC disk electrode, that is, the substrate electrode for the preparation of a-MnO 2 -AB thin-lm WEs. 17 On the other hand, according to McCrory et al, 157 for metal oxide catalysts in NaOH and KOH solutions C s values ranging from 0.022 mF cm À2 to 0.130 mF cm À2 are reported, [220][221][222][223][224][225][226][227][228][229][230][231][232] thus the C s value based on the bare GC disc electrode, that was used in our work, is well within this range. However, since original (untreated) data to all This journal is © The Royal Society of Chemistry 2022…”

Porous FeP/CoP heterogeneous materials as efficient alkaline oxygen evolution reaction (OER) catalysts

“…At present, the best way to reduce the energy barrier is to use noble metal-based catalysts. 7,8 However, the high cost and scarcity of precious metals make it difficult for large scale applications. Therefore, the development of low-cost and efficient OER catalysts is a research hotspot.…”

Polyaniline-wrapped MnMoO4as an active catalyst for hydrogen production by electrochemical water splitting

“…Considering these loop holes, developing low-cost electrocatalysts with excellent activity and stability became an intensive research area. To date, transition metal-based oxides, 14 phosphates, 15 metal dichalcogenides, [16][17][18][19][20] and lithium-containing transition metal oxides 21 have been widely studied for water splitting. Among them, binary/ternary transition metal oxides with diverse oxidation numbers have attracted substantial interest compared to monometallics due to the accessibility of various redox processes, which may enhance the electrochemical activity of the electrocatalyst.…”