Role of Fe-O-M Bond in Controlling the Electroactive Species Generation from the FeMO4(M: Mo and W) Electro(pre)catalyst during OER

Mrinal Kanti Adak, Anubha Rajput, Dibyajyoti Ghosh, Biswarup Chakraborty

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

While bulk or surface modification of transition-metal-based pre-catalysts is the most obvious reason of their superior activity during alkaline oxygen evolution reaction (OER), identification of electroactive species and accurately establishing the in situ evolution pathway of such species remain challenging, albeit fundamentally important to correlate the electronic structure with their inherent activity. Given that, a detailed electrochemical OER study with two bimetallic FeIIMVIO4(M = Mo and W) type electrocatalysts has been performed, and the influence of M in the electronic structure at the molecular level to control the energetics of the electroactive species formation has been studied. FeMoO4turns out to be better compared to its isotypic FeWO4which is due to facile electrokinetics to evolve the electroactive species. Post-chronoamperometric characterization and time-dependent quasi in situ Raman analyses reveal a potential-driven hydrolytic dissolution of [MoO4]2-from FeMoO4to form α-FeO(OH) as the electroactive species. Poor lattice stability (formation enthalpy; ΔHf), weak Fe-O-Mo bonding, and low decomposition enthalpy (ΔHD) of the FeMoO4lattice favor a facile electrocatalytic decomposition to evolve the highly reactive FeO(OH) surface in which the peroxo (O-O) bond formation is rate limiting with a minimum potential barrier of 38 kJ mol-1obtained from the variable temperature OER study. Under a very similar electrochemical condition, FeWO4is relatively robust, with negligible [WO4]2-leaching due to a high ΔHDvalue and less ionic character of the Fe-O-W bonds. This combined experimental and theoretical study establishes how the material's electronic structure, that is, the bonding between the anionic counterpart and the active metal, can play an intriguing role to influence the OER activity which is so far relatively less well-explored.

Original languageEnglish
Pages (from-to)13645-13660
Number of pages16
JournalACS Applied Energy Materials
Volume5
Issue number11
DOIs
StatePublished - 28 Nov 2022
Externally publishedYes

Keywords

  • electrokinetic OER
  • electronic-structure
  • in situ structural evolution FeMO
  • lattice energy
  • time-resolved Raman

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrochemistry
  • Materials Chemistry
  • Electrical and Electronic Engineering

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