Catalysis of the Oxygen Evolution Reaction by 4–10 nm Cobalt Nanoparticles

Adiga

et al. 2021

Small

the redox of these metals during cycling, such as in RuO 2 [14] and Ni-based oxides, [15] can be used to estimate their surface concentration. The density of active sites is often simply approximated by the exposed geometric surface area (measured by, e.g., microscopy or N 2 adsorption [16] ) or the electrochemical surface area (ECSA) by assumptions regarding intrinsic capacitance. [15,[17][18][19] However, all of these normalization approaches imply that electrochemical activity is governed exclusively by the terminal surface layer of the oxide, without serious consideration of sub-surface layers that may influence activity as well.Size effects in the OER activity of nanoparticles, [20,21] thickness-dependent effects in thin films, [22] and substrate-dependent effects in 2D materials [23] imply that while a catalytic reaction occurs at the catalyst/electrolyte interface, the supporting layers of a catalyst (and/or its support) can influence activity as well. For oxides, these size effects can include manipulating the ability of transition metal sites to oxidize prior to the onset of OER. [20,21] Thickness effects can additionally include charge transfer to/from a support, [24][25][26] quantum tunneling through ultra-thin layers, [27,28] and formation of a Electrocatalytic reactions are known to take place at the catalyst/electrolyte interface. Whereas recent studies of size-dependent activity in nanoparticles and thickness-dependent activity of thin films imply that the sub-surface layers of a catalyst can contribute to the catalytic activity as well, most of these studies consider actual modification of the surfaces. In this study, the role of catalytically active sub-surface layers was investigated by employing atomicscale thickness control of the La 0.7 Sr 0.3 MnO 3 (LSMO) films and heterostructures, without altering the catalyst/electrolyte interface. The activity toward the oxygen evolution reaction (OER) shows a non-monotonic thickness dependence in the LSMO films and a continuous screening effect in LSMO/SrRuO 3 heterostructures. The observation leads to the definition of an "electrochemically-relevant depth" on the order of 10 unit cells. This study on the electrocatalytic activity of epitaxial heterostructures provides new insight in designing efficient electrocatalytic nanomaterials and core-shell architectures.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202103632.

mentioning

confidence: 99%

Contribution of the Sub‐Surface to Electrocatalytic Activity in Atomically Precise La_0.7Sr_0.3MnO₃ Heterostructures

Adiga

et al. 2021

Small

“…The observed activation energies for the reduction of Co 3 O 4 -like clusters or nanoparticles to CoO and the following reduction of CoO to Co are shown in Table 2 for some catalysts supported on H-ZSM- The yields of oxygen obtained in the presence of catalysts 1%Со(6)-Z(s) are shown in Table 3 (samples Nos. [1][2][3][4]. Under identical conditions, the maximal yield of oxygen (64 % of the stoichiometry of reaction (IV)) was observed with the catalyst supported on ZSM-5 zeolite.…”

Section: Resultsmentioning

confidence: 99%

“…Five series of Co-ZSM-5 catalysts were prepared by this method. In the first series, the NH 4 OH/Co 2+ () ratio was varied (3,6,10,15,20,30) by varying the ammonia concentration at the constant cobalt content (1 wt %). H-ZSM-5 zeolite with Si/Al=17, 95 % crystallinity and no more than 0.09 wt % of Fe impurity was used for the preparation.…”

Section: Catalyst Preparationmentioning

confidence: 99%

See 1 more Smart Citation

Co(II, III) Hydroxides Supported on Zeolite Acting as an Efficient and Robust Catalyst for Catalytic Water Oxidation with Ru(bpy)33+

Yashnik,

Chikunov,

Taran

et al. 2019

Top Catal

A novel highly efficient and stable for many cycles catalyst (1%Со-ZSM-5(17)) for water oxidation was developed using the method of polycondensation for stabilization of oxo/hydroxo complexes of cobalt (II, III) and nanosize Co 3 O 4 in zeolite channels. In a weak-alkaline medium (pH 8.0, 9.2, 10.0) in the presence of a oneelectron oxidant (Ru(bpy) 3 3+), the catalyst provided the yield of oxygen as high as 56, 73 и 78 % of the stoichiometric quantity, respectively. Catalysts based on ZSM-5 zeolite exhibited higher catalytic activity as compared to the catalysts based on the MOR, BEA, Y. Inspection of the electron states of cobalt in the Co-containing zeolitebased catalysts using TPR-H 2 and UV-Vis DR techniques revealed that α-Co(OH) 2-like polynuclear clusters and hydrocomplexes stabilized in the zeolite channels were most active to catalytic oxidation of water, while their transformation to Co 3 O 4-like clusters/nanoparticles and Co 2+ oxocomplexes, respectively, during thermal treatment led to some decrease in the catalyst efficiency. Coarsening of Co 3 O 4-like clusters/nanoparticles caused the further decrease in the system efficiency. The minimal activity was observed with the catalysts containing predominantly isolated Co 2+ Oh ions. The result obtained indicates a kind of at least polynuclear structure of the catalytically active center Co n O x , where n > 2.

“…The calculated TOF values are comparable to previous results reported in literature. [52][53][54] For example, Cao et al 54 stated TOF values between 0.05 and 4.0 s −1 at 1.6 V vs. RHE for CoO x /PCN and RuO x catalysts. The presented method to determine the TOF based on a geometric approach has a great potential for the evaluation of electrocatalysts and aims for the elucidation of structure-activity relationships.…”

Section: Electrochemical Performancementioning

confidence: 99%

Particle size-controlled synthesis of high-performance MnCo-based materials for alkaline OER at fluctuating potentials

Broicher

Klingenhof

Frisch

et al. 2021

Catal. Sci. Technol.