Unraveling the Role of CeO₂ in Stabilization of Multivalent Mn Species on α-MnO₂/Mn₃O₄/CeO₂/C Surface for Enhanced Electrocatalysis

Abstract

A hybrid heteronanostructure of α-MnO 2 /Mn 3 O 4 /CeO 2 with the atomic-level coupled nanointerface entrenched in Vulcan carbon is reported and explored for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). CeO 2 plays an essential role in increasing the surface Mn 2+/3+/4+ in α-MnO 2 /Mn 3 O 4 /CeO 2 /C for ORR/OER processes. It shows enhanced bifunctional activity, superior to that of the benchmark 20 wt % Pt/C and Pd/C catalysts. It displays an ORR onset potential of −0.13 V (vs Ag/AgCl), limiting current density of −6.63 mA cm −2 (at 1600 rpm), mass-specific current of 47.6 mA mg MO −1 with a lower Tafel slope (921.9 mV dec −1 ), and an inclusive 4-e transfer involved in ORR. The OER onset potential and current density are 0.58 V (vs Ag/AgCl) and 8.45 mA cm −2 (at 0.8 V). The unique hybrid structure with oxide−oxide interface in α-MnO 2 / Mn 3 O 4 /CeO 2 is correlated to explain the mechanistic pathway. Multistate Mn(II/III/IV) and Ce(III/IV) synergistically influence in tendering superior activity with enhanced stability.

Nonprecious Hybrid Metal Oxide for Bifunctional Oxygen Electrodes: Endorsing the Role of Interfaces in Electrocatalytic Enhancement

“…17 CeO 2 is a potential additive for improving the activity of a transition MO owing to its unique oxygen storage capacity, oxygen transfer ability, and highly active Ce 3+ /Ce 4+ redox couple. 18,19 Equation 1 shows the ability of CeO 2 to reversibly switch between the +3 and the +4 oxidation states: 18,20 The properties of CeO 2 defined it as an "oxygen buffer" that regulates the surface oxygen density by capturing or eliminating oxygen in O 2 -rich or O 2 -lean conditions, respectively, thereby generate oxygen vacancies and promotes rapid electron transfer across the oxide−oxide/carbon interface. 20−22 For instance, Liu et al 20 synthesized Co 3 O 4 −CeO 2 / KB, which was found to be very efficient as compared to that of single MO counterparts due to the strong synergistic interaction between Co 3 O 4 and CeO 2 .…”

“…This is due to the formation of robust heterogeneous interfaces between different phases of MOs and their synergetic effects which promotes easy electron transfer . CeO 2 is a potential additive for improving the activity of a transition MO owing to its unique oxygen storage capacity, oxygen transfer ability, and highly active Ce 3+ /Ce 4+ redox couple. , Equation shows the ability of CeO 2 to reversibly switch between the +3 and the +4 oxidation states: , …”

Oxygen Vacancy‐Enhanced Ternary Nickel‐Tungsten‐Cerium Metal Alloy‐Oxides for Efficient Alkaline Electrochemical Full Cell Water Splitting Using Anion Exchange Membrane

“…The influence of multivalent states of Ni (+2, +3), Ce (+3, +4), and W (0, +4, +5, +6, +x) on electrocatalysis activity is mainly based on the following aspects. (1) The internal conversion between multivalent states in Ni (+2, +3), Ce (+3, +4), and W (0, +4, +5, +6, +x) leads to rapid charge transfer for carriers, which enhances the conversion of H‐H 2 and the dissociation of chemical bonds between O−H to improve the catalytic activity [54–58] . (2) The synergistic effect and alloying between the multivalent states of transition metals Ni, Ce, and W enhance the catalytic activity [57–59] .…”

“…[54][55][56][57][58] (2) The synergistic effect and alloying between the multivalent states of transition metals Ni, Ce, and W enhance the catalytic activity. [57][58][59] (3) The existence of oxygen vacancies will expose more active sites, which will promote the interaction between activated electrons and protons to improve the catalytic activity. [60,61] The X-band paramagnetic resonance (EPR) in Figure S4 also displays a significantly stronger EPR signal with g factor close to 2 in NiCeWO x -1 compared to that of NiCeWO x -2.…”

Enhanced Electrocatalytic Activity of Cobalt-Doped Ceria Embedded on Nitrogen, Sulfur-Doped Reduced Graphene Oxide as an Electrocatalyst for Oxygen Reduction Reaction

“…Precious metals like Pt and Pd supported on CeO 2 exhibit good catalytic activity toward the ORR [21][22][23][24], but precious metals are quite challenging for commercialization [25,26]. Although there is much research dealing with CeO 2 -supported catalysts for the ORR, there are very few studies focusing on the importance of oxygen vacancy in doped CeO 2 [27][28][29]. Furthermore, the abundance of oxygen vacancies in CeO 2 favors O 2 adsorption and oxygen conductivity due to the coexistence of Ce 4+ and Ce 3+ , which contribute to the CeO 2 -supported electrocatalyst in the ORR [30,31].…”