Cation Substitution Induced d‐Band Center Modulation on Cobalt‐Based Spinel Oxides for Catalytic Ozonation

Abstract

Co3O4 spinel is a promising transition metal oxide (TMO) catalyst for the catalytic ozonation of volatile organic compounds (VOCs). Herein, metal–organic frameworks (MOFs)‐derived Ni‐ and Mg‐ substituted Co3O4 catalysts retain similar spinel structures, but display improved and reduced ozonation performance of methyl mercaptan (CH3SH), respectively. Remarkably, the NiCo2O4 catalyst can still ≈90% removal of CH3SH after running for 20 h at room temperature under an initial concentration of 50 ppm CH3SH and 40 ppm O3, relative humidity of 60%, and space velocity of 300 000 mL h−1 g−1, exceeding the reported values. Experimental characterizations have unveiled that the substitution of Ni and Mg into the Co3O4 spinel altered surface acidity, oxygen species mobility, and Co2+/Co3+ ratio. The in situ Raman spectra reveal the dynamic formation Co(III)‐Oad* via the transformation of O3 into surface atomic oxygen (Oad*) and peroxide species (O2*). Theoretical calculations verify that Ni‐substitution increases nonuniform charges and Fermi density, leading to a moderate increase in d‐band center energy levels, thereby promoting O3 specific adsorption/activation to convert Oad*/O2* and •OH/1O2/•O2−, which contributes to eliminate CH3SH and prevent poisoning. The concept of tuning the d‐band center can provide valuable insights for the design of other catalysts for catalytic ozonation.

Tuning the d-Band Center of Co3O4 via Octahedral and Tetrahedral Codoping for Oxygen Evolution Reaction

“…It is widely accepted that the d-band center (ε d ) can be used as a descriptor of the transition metal binding adsorbate tendency. − The ε d level of the adsorption Co sites for Co 3 O 4 , Al–Co 3 O 4 , Ga–Co 3 O 4 , Fe–Co 3 O 4 , Ni–Co 3 O 4 , and In–Co 3 O 4 is −2.446, −2.820, −2.795, −2.543, −2.786, and −2.391 eV, respectively (Figure a–c and Table S12). The PDS energy barriers should present a reverse volcanic trend versus the d-band center of the adsorption Co sites (Figure i).…”

Modulation Strategies and Activity Descriptors of Spinel Electrocatalysts for Lithium−Oxygen Batteries

“…Qu et al. optimized the electronic structure of Co 3 O 4 spinel by different cation substitutions, thus selecting spinel materials with high catalytic activity [119] . As seen in Figure 6a, the density of states (DOS) of the spinel materials is clearly observed, three samples possess a high DOS at E f , which show strong metallicity, suggesting a fast electron transfer in MCo 2 O 4 (M=Co, Ni, Mg).…”

“…(h) Electron density difference diagram of reactants adsorption at the Co site on various catalyst surfaces. (a–c) Reproduced with permission [119] . Copyright 2023, Wiley‐VCH.…”

Synergy of W doping and oxygen vacancy engineering on d-band center modulation for enhanced gas sensing performance

“…28 It has been reported that a versatile electronic structure can be achieved by controlling the vacancy concentration and selecting the substitution of either A-site or B-site ions. 29,30 However, there is limited research on the effect of selective replacement of metal ions at the octahedral site in NiCo 2 O 4 on its gas sensing capabilities.…”