Push‐Pull Electronic Effects in Surface‐Active Sites Enhance Electrocatalytic Oxygen Evolution on Transition Metal Oxides

Abstract

Sustainable electrocatalysis of the oxygen evolution reaction (OER) constitutes a major challenge for the realization of green fuels. Oxides based on Ni and Fe in alkaline media have been proposed to avoid using critical raw materials. However, their ill-defined structures under OER conditions make the identification of key descriptors difficult. Here, we have studied FeÀ NiÀ Zn spinel oxides, with a well-defined crystal structure, as a platform to obtain general understanding on the key contributions. The OER reaches maximum performance when: (i) Zn is present in the Spinel structure, (ii) very dense, equimolar 1 : 1 : 1 stoichiometry sites appear on the surface as they allow the formation of oxygen vacancies where Zn favors pushing the electronic density that is pulled by the octahedral Fe and tetrahedral Ni redox pair lowering the overpotential. Our work proves cooperative electronic effects on surface active sites as key to design optimum OER electrocatalysts.

Enhancement of electrocatalytic oxygen evolution by chiral molecular functionalization of hybrid 2D electrodes

“…The Ni 9 FeO x catalyst shown in Fig. 2b was deposited on a Ni foam using a combustion method 44 . The ECSA was obtained from the determination of the adsorption capacitance 34 .…”

Quasi‐Parallel NiFe Layered Double Hydroxide Nanosheet Arrays for Large‐Current‐Density Oxygen Evolution Electrocatalysis

“…The change in the content of trivalent metal cations with the evolution in the alignment of nanoarrays is interesting but seldom reported. As a strong Lewis acid, Fe 3+ would withdraw the adjacent electrons from Ni 2+ sites via an electronic pulling effect, which enhances the stability of catalytically active Ni 3+ species in the catalyst [45–48] . In particular, a high content of surface Ni 3+ species, which is induced by pre‐activation or synergistic electronic interactions, is considered to be a prerequisite for OER activity [49–51] .…”

Enhancement of Electrocatalytic Oxygen Evolution by Chiral Molecular Functionalization of Hybrid 2D Electrodes

“…2. The Ni9FeOx catalyst was deposited on Ni foils using a combustion method introduced elsewhere 40 . The ECSA was obtained from the determination of the specific adsorption capacitance 30 .…”

“…Monolayer NiOx islands were synthesized by liquid exfoliation from the bulk counterparts reported elsewhere 58,59 and spin-coated on Au(111) film on mica substrates (epitaxial gold on mica, Georg Albert PVD -Beschichtungen). Ni9FeOx on Ni foil electrodes were synthesized using a combustion method 40 .…”