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Oxygen evolution reaction (OER) is a vital electrochemical process for various energy conversion and fuel production technologies. Co/Ni‐rich perovskite oxides are extensively studied as promising alternatives to precious‐metal catalysts; however, low‐cost and earth‐abundant iron (Fe)‐rich perovskites are rarely investigated to date due to their poor activity and durability. This study reports an Fe‐rich Sr0.95Ce0.05Fe0.9Ni0.1O3−δ (SCFN) perovskite oxide with minor Ce/Ni co‐doping in A/B sites as a high‐performance OER electrocatalyst. Impressively, SCFN shows more than an order of magnitude enhancement in mass‐specific activity compared to the SrFeO3−δ (SF) parent oxide, and delivers an attractive small overpotential of 340 mV at 10 mA cm−2, outperforming many Co/Ni‐rich perovskite oxides ever reported. Additionally, SCFN displays robust operational durability with negligible activity loss under alkaline OER conditions. The increased activity and stability of SCFN can be ascribed to co‐doping‐induced synergistic promotion between structural and electronic modulation, where Ce doping facilitates the formation of a 3D corner‐sharing cubic structure and Ni doping gives rise to strong electronic interactions between active sites, which is key to achieving a highly active long‐life catalyst. Importantly, this strategy is universal and can be extended to other Fe‐based parent perovskite oxides with high structural diversity. [ABSTRACT FROM AUTHOR]

Abstract: Active and affordable electrocatalysts made from Earth‐abundant elements are central to water electrolysis involving the oxygen evolution reaction (OER). While nonprecious transition metal‐based (Co, Ni, Fe) materials are extensively studied as cost‐effective, high‐performance alternatives to noble metal‐based catalysts, iron‐based catalysts with Fe acting as the single active site are rarely investigated due to their intrinsically low reactivity. Here, by taking advantage of the versatility of perovskite structure, metalloid Si, the second most abundant element in Earth's crust, is doped into an Fe‐based perovskite oxide (SrFeO3−δ), to obtain SrFe0.9Si0.1O3−δ as a highly efficient OER catalyst. Remarkably, SrFe0.9Si0.1O3−δ shows an approximately threefold growth in OER activity relative to SrFeO3−δ with a small Tafel slope of 58 mV dec−1, comparing favorably to or even exceeding many Co‐/Ni‐based perovskite catalysts. This enhancement can be ascribed to a structural transition from tetragonal to cubic symmetry upon Si‐doping, which brings about an optimized iron oxidation state, rich oxygen vacancies, and fast charge transfer that are beneficial to the OER catalysis. This work highlights the importance of how incorporating Earth‐abundant, nonprecious elements (e.g., Si) into a perovskite oxide structure can be used to create novel materials for the electrochemical water oxidation. [ABSTRACT FROM AUTHOR]

The perovskite SrNb0.1Co0.7Fe0.2O3− δ (SNCF) is a promising OER electrocatalyst for the oxygen evolution reaction (OER), with remarkable activity and stability in alkaline solutions. This catalyst exhibits a higher intrinsic OER activity, a smaller Tafel slope and better stability than the state-of-the-art precious-metal IrO2 catalyst and the well-known BSCF perovskite. The mass activity and stability are further improved by ball milling. Several factors including the optimized eg orbital filling, good ionic and charge transfer abilities, as well as high OH− adsorption and O2 desorption capabilities possibly contribute to the excellent OER activity. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is of prime importance in multiple energy storage devices. Perovskite oxides involving lattice‐oxygen oxidation are generally regarded as highly active OER catalysts, but the deprotonation of surface‐bound intermediates limit the further activity improvement. Here, it is shown that this kinetic limitation can be removed by introducing Sr3B2O6 (SB) which activates a proton‐acceptor functionality to boost OER activity. As a proof‐of‐concept example, an experimental validation is conducted on the extraordinary OER performance of a Sr(Co0.8Fe0.2)0.7B0.3O3−δ (SCFB‐0.3) hybrid catalyst, made using Sr0.8Co0.8Fe0.2O3−δ as active component and SB as a proton acceptor. This smart hybrid exhibits an exceptionally ultrahigh OER activity with an extremely low overpotential of 340 mV in 0.1 m KOH and 240 mV in 1 m KOH required for 10 mA cm−2 which is the top‐level catalytic activity among metal oxides reported so far, while maintaining excellent durability. The correlation of pH and activity study reveals that this enhanced activity mainly originates from the improved interfacial proton transfer. Such a strategy further demonstrated to be universal, which can be applied to enhance the OER activity of other high covalent oxides with close O 2p‐band centers relative to Fermi energy. [ABSTRACT FROM AUTHOR]

Development of electrocatalysts for the oxygen evolution reaction (OER) plays a critical role in electrochemical water splitting systems. Perovskite oxides represent one category of efficient catalysts for the OER, among which Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF) has been extensively studied. In this work, we discussed the effect of synthesis approaches on the OER performance of BSCF. Three routes, including solution combustion, sol-gel process and solid-state reaction, were applied to synthesize the bulk-sized BSCF perovskites, denoted as BSCF-SC, BSCF-SG and BSCF-SS, respectively. Electrochemical measurements revealed varied OER performance, with BSCF-SS showing the highest intrinsic activity much better than that of BSCF-SC and BSCF-SG. The activity difference may originate from the variation in the surface oxidation states of the B-site cobalt cations. Moreover, all the BSCF perovskites exhibited comparably good stability in catalyzing the OER. In light of the simplicity, the viability for scale-up and the high activity of BSCF-SS, solid-state reaction may be a suitable way for fabricating highly-active BSCF electrocatalyst. This study could provide new insight into enhanced oxygen evolution on perovskite oxides by selecting an optimized synthesis approach. [ABSTRACT FROM AUTHOR]

Development of an oxygen electrode with high stability and good electrochemical activity is critical to achieve the practical applications of rechargeable lithium-oxygen batteries (LOBs) in our daily life. here, we report the facile synthesis of a graphene-based composite as an efficient dual function precious-metal-free electrocatalyst for LOBs by applying graphite oxide as the graphene precursor, aniline as the carbon and nitrogen source, FeCl 3 and Co(NO 3 ) 2 ·6H 2 O as the cation sources and argon as the atmosphere during the pyrolysis. Scanning electron microscope and transmission electron microscope observations demonstrate that the as-prepared electrocatalyst is composed of graphene sheets with nanoparticles mainly in the size of 20-50 nm, while X-ray diffraction characterization confirms that the sample is composed of multiple species such as carbon, cobalt/iron oxide, cobalt/iron sulfide and metallic iron. The cyclic voltammetry and linear sweep voltammograms tests of the electrocatalyst demonstrate favorable electrocatalytic activity for both oxygen reduction and evolution reactions, suggesting its bifunctionality. With the electrocatalyst/Ketjen Black (KB) oxygen electrode applying in LOBs, a specific capacity of 4772 mAh g KB −1 and a discharge plateau potential of ∼2.75 V are reached at the density of 100 mA g KB −1 for the related LOBs by discharging to 2.0 V and charging to 4.4 V. [ABSTRACT FROM AUTHOR]