Grasping periodic trend and rate-determining step for S-modified metals of metal sulfides deployable to produce OH via H2O2 cleavage
- Grasping periodic trend and rate-determining step for S-modified metals of metal sulfides deployable to produce OH via H2O2 cleavage
- 이승철; 김상훈; 김종식; 최윤정; Satadeep Bhattacharjeed
- Issue Date
- Applied catalysis B, Environmental
- VOL 253-68
- Iron sulfides are fascinating catalytic phases because these include S-modified Feδ+ (δ  ≤  2) species functioning as H2O2 activators to form OH used for oxidatively degrading aqueous contaminants (e.g., phenol). As an initial step for locating S-modified metal species (Mδ+) that outperform Feδ+ in catalytic H2O2 cleavage, hexagonal metal sulfides (MS) were synthesized using Mn, Fe, Co, Ni, and Cu to understand electric potential-assisted H2O2 scission kinetics on Mδ+ species. Niδ+ species were found to show the greatest OH productivity among all Mδ+ species studied, mainly resulting from the Lewis acidic nature of Niδ+ species adequate to expedite the liberation of OH species. This was partially evidenced by H2O2 activation/phenol degradation runs on Mδ+ species, wherein initial H2O2 activation rate (-rH2O2,0) or initial phenol degradation rate (-rPHENOL,0) of Niδ+ species was 3– 9 times those of the other Mδ+ species. Niδ+ species, therefore, were located in the middle of the volcano-shaped curve plotting -rH2O2,0 (or -rPHENOL,0) versus the type of Mδ+. Kinetic assessment of Mδ+ species under fine-tuned reaction environments also showed that regardless of varying H2O2 concentrations, Mδ+ species were found to retain their -rH2O2,0 values in the absence of electric potentials. Conversely, Mδ+ species could enhance -rPHENOL,0 values at larger electric potentials, where greater energies were likely exerted on Mδ+ species. This indeed corroborated that OH desorption from Mδ+ species was the rate-determining step to direct catalytic H2O2 scission. In addition to heterogeneous catalytic nature of Niδ+ species in fragmenting H2O2, outstanding H2O2 scission ability provided by Niδ+ species could also compensate for their moderate catalytic stability at pH-neutral condition.
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