Unveiling the occurrence of Co(III) in NiCo layered electroactive hydroxides: the role of distorted environments sight into the electronic structure behavior of Ni(II)-Co(II) layered hydroxides

MARTÍN MIZRAHI; HUNT DIEGO; FÉLIX G REQUEJO; OESTREICHER, VÍCTOR; JOBBAGY, MATÍAS

Conferencia; 30th Annual Users? Meeting of LNLS; 2020

Co‐ and Ni‐basedlayered hydroxides constitute a unique class of two‐dimensionalinorganic materials with exceptional chemical diversity,physicochemical properties and outstanding performance assupercapacitors and overall water splitting catalysts. Recently, theoccurrence of Co(III) in these phases has been proposed as a keyfactor that enhance their electrochemical performance. However, theorigin of this centers and control over its contents remains as anopen question. We employed the Epoxide Route to synthesize a wholeset of α‐NiCo layered hydroxides. The PXRD and XAScharacterization alert about the occurrence of Co(III) as aconsequence of the increment in the Ni content. DFT+U simulationsuggest that the shortening of the Co?O distance promotes astructural distortion in the Co environments, resulting in a doubledegeneration in the octahedral Co 3d orbitals. Hence, a strongmodification of the electronic properties leaves the system prone tooxidation, by the appearance of Co localized electronic states on theFermi level. This work combines a microscopic interpretationsupported by a multiscale crystallochemical analysis, regarding theso called synergistic redox behavior of Co and Ni, offeringfundamental tools for the controllable design of highly efficientelectroactive materials. To the best of our knowledge this is thefirst computational‐experimental investigation of the electronicand structural details of α‐NiCo hydroxides, laying the foundationfor the fine tuning of electronic properties in layered hydroxides.p { margin-bottom: 0.25cm; line-height: 120% }