Structure Sensitivity of the Oxygen Evolution Reaction Catalyzed by Cobalt(II,III) Oxide

Abstract

Quantum chemical calculations and simulated kinetics were used to examine the structure sensitivity of the oxygen evolution reaction on several surface terminations of Co3O4. Active sites consisting of two adjacent Co(IV) cations connected by bridging oxos were identified on both the (001) and (311) surfaces. Formation of the O-O bond proceeds on these sites by nucleophilic attack of water on a bridging oxo. It was found that the relative turnover frequencies for the different sites are highly dependent on the overpotential, with the dual-Co site on the (311) surface being most active at medium overpotentials (0.46-0.77 V), where O-O bond formation by water addition is rate limiting. A similar dual-Co site on the (001) surface is most active at low overpotentials (<0.46 V), where O2 release is rate limiting, and a single-Co site on the (110) surface is most active at overpotentials that are high enough (>0.77 V) to form a significant concentration of highly reactive terminal Co(V)═O species. Two overpotential-dependent Sabatier relationships were identified based on the Brønsted basicity and redox potential of the active site, explaining the change in the active site with overpotential. The (311) dual-Co site that is most active in the medium overpotential range is consistent with recent experimental observations suggesting that a defect site is responsible for the observed oxygen evolution activity and that a modest concentration of superoxo intermediates is present on the surface. Importantly, we find that it is essential to consider the kinetics of the water addition and O2 release steps rather than only the thermodynamics.

Enhanced Water Oxidation Activity of the Cobalt(II,III) Oxide Electrocatalyst on an Earth‐Abundant‐Metal‐Interlayered Hybrid Porous Carbon Support

“…Notably, both in‐plane and out‐of‐plane orientations can be controlled by choosing the support and the deposition parameters, as observed for other electrodeposited oxide films . The activities of the various planes of Co 3 O 4 are different due to dissimilar packing densities and electronic structures . This leads to variations in reactivity, depending on the ratio of exposed surfaces, as the reactivity is dependent on the exposed surfaces as well as the potential .…”

“…[6,16] The activities of the various planeso fC o 3 O 4 are different due to dissimilar packing densitiesa nd electronic structures. [17] This leads to variations in reactivity, depending on the ratio of exposed surfaces, [18] as the reactivity is dependent on the exposed surfaces as well as the potential. [17] Though thermala nd electrochemical oxidation of electrode-positedC ol eads to the formation of Co 3 O 4 ,i td oes not lead to oxidation of the Cu interlayer,a so bserved by XRD (Figure 3).…”

“…[17] This leads to variations in reactivity, depending on the ratio of exposed surfaces, [18] as the reactivity is dependent on the exposed surfaces as well as the potential. [17] Though thermala nd electrochemical oxidation of electrode-positedC ol eads to the formation of Co 3 O 4 ,i td oes not lead to oxidation of the Cu interlayer,a so bserved by XRD (Figure 3). The Co 2p XPS shows peaks at bindinge nergies of about 780-782, 786, and 796-797 eV,w hich correspond to the Co 2p 3/2 ,C o2ps atellite, andC o2p 1/2 peaks, respectively (Figure 4a).…”

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

“…The short-range order of the amorphous structure provides a large fraction of surface-exposed defects that act as catalytic active sites. [138,139] The expectation of high efficiency resulting from the abundant active sites has triggered numerous studies on amorphous metal oxide catalysts. Moreover, some studies have reported that the amorphous phase has advantages in terms of mechanical and electrochemical stability as the disordered structure offers structural stability.…”

SnO2 -TiO2 structures and the effect of CuO, CoO metal oxide on photocatalytic hydrogen production

“…On the other hand, the presence of co‐catalyst (CuO or CoO) improves the photocatalytic activity of hydrogen production, due to formation of the p‐n heterojunction that effectively separates charge carriers. It is worth mentioning that CuO and CoO played different roles during the process: while CoO is expected to catalyze the O 2 evolution reaction, CuO is expected to catalyze the H 2 evolution reaction . However, the improvement by coupling ST with CuO is considerably greater than that obtained when the material is modified with CoO, indicating that reduction reaction is the controlling step in the photocatalytic process.…”