Spectroscopic Study of Sediments from Chapala Lake in Western Mexico

Arízaga, Gregório Guadalupe Carbajal; Doumer, Marta Eliane; Lucio, Guillermo Alvarez; Salazar, Sonia; Mangrich, Antônio S.; Huerta, A.

doi:10.1007/s10812-016-0380-4

Cited by 3 publications

(1 citation statement)

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“…We further performed X‐band electron paramagnetic resonance spectroscopy (EPR) to show the difference in electronic structures of the NiFeCr‐6:2:1, NiFe‐3:1, and NiCr‐2:1 LDH samples and confirm the stability before and after OER measurement ( Figure 4 ). The intense and broad g = 2.0 signal in NiFe‐3:1 sample was indicative of the high‐spin Fe 3+ sites in the octahedral symmetry (3d 5 electronic configuration, S = 5/2 electronic spin) . The weak g = 2.2 signal in NiCr‐2:1 sample was indicative of the Cr 3+ sites in the octahedral symmetry (3d 3 electronic configuration, S = 3/2 electronic spin) .…”

Section: Resultsmentioning

confidence: 98%

Highly Active Trimetallic NiFeCr Layered Double Hydroxide Electrocatalysts for Oxygen Evolution Reaction

Yang

Dang

Shearer

et al. 2018

Advanced Energy Materials

595

307

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rechargeable metal-air batteries. [1,2] This reaction demands efficient electrocatalysts that can accelerate the reaction rate, lower the overpotential, and remain stable over time. Currently, noble-metal-based compounds such as IrO 2 and RuO 2 provide good OER performance under alkaline conditions, but their large-scale application is restricted by their scarcity and high cost. [3] Accordingly, much research effort has been devoted to the development of high-performance earth-abundant OER electrocatalysts based on transition-metal elements, usually in the form of metal oxides or metal (oxy)hydroxides, that are inexpensive and stable upon prolonged exposure under oxidizing conditions. [4][5][6][7] In addition to the synergistic effects of transition metals and electrical conductivity, the intrinsic activities of these transition metal oxide or (oxy)hydroxide OER catalysts are closely connected to the number of 3d electrons of the metals; the surface transition-metal ions exhibited e g orbitals which could bond with surfaceanion adsorbates and then influence the binding of oxygenic intermediates. [8,9] The binding strength of these intermediates is thought to dictate catalytic activity. [10] Identifying the relationship between OER activity and the catalyst electronic structure can provide a simple rationale for gaining mechanistic insights and finding new design strategies for the earth-abundant OER catalysts.Among various transition metal-based OER catalysts, metal layered double hydroxides (LDHs) and oxyhydroxides have attracted much attention because of their abundance in the earth's crust and their considerable catalytic activity. [5,6,[11][12][13][14][15][16][17][18][19][20][21] NiFe LDH and more generally NiFe (oxy)hydroxides have emerged as the most active OER catalyst compared to other bimetallic earth-abundant LDHs under basic conditions, [6,15,17,22] and several studies have been directed at understanding the role of Fe in increasing the OER intrinsic activity of NiFe-containing (oxy) hydroxide materials. [23] Boettcher and co-workers demonstrated that Fe incorporation into NiOOH lattice enhances the electronic conductivity in the film and Fe exerts a partial-chargetransfer activation effect on Ni centers throughout the catalyst film, but the enhanced catalytic efficiency cannot be completely explained. [17] To better understand the role of Fe, they further studied other incorporated metal cations (Mn, Ti, Ce, Fe, and La) in NiO x H y , finding that only Fe permanently increases the OER The development of efficient and robust earth-abundant electrocatalysts for the oxygen evolution reaction (OER) is an ongoing challenge. Here, a novel and stable trimetallic NiFeCr layered double hydroxide (LDH) electrocatalyst for improving OER kinetics is rationally designed and synthesized. Electrochemical testing of a series of trimetallic NiFeCr LDH materials at similar catalyst loading and electrochemical surface area shows that the molar ratio Ni:Fe:Cr = 6:2:1 exhibits the best intrinsic OER catalytic activity ...

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Section: Resultsmentioning

confidence: 98%