Monovalent, trivalent and tetravalent nickel

The electrolysis of water is of global importance to store renewable energy and the methodical design of next-generation oxygen evolution catalysts requires a greater understanding of the structural and electronic contributions that give rise to increased activities. Herein, we report a series of Ruddlesden–Popper La0.5Sr1.5Ni1−xFexO4±δ oxides that promote charge transfer via cross-gap hybridization to enhance electrocatalytic water splitting. Using selective substitution of lanthanum with strontium and nickel with iron to tune the extent to which transition metal and oxygen valence bands hybridize, we demonstrate remarkable catalytic activity of 10 mA cm−2 at a 360 mV overpotential and mass activity of 1930 mA mg−1ox at 1.63 V via a mechanism that utilizes lattice oxygen. This work demonstrates that Ruddlesden–Popper materials can be utilized as active catalysts for oxygen evolution through rational design of structural and electronic configurations that are unattainable in many other crystalline metal oxide phases.

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Exceptional electrocatalytic oxygen evolution via tunable charge transfer interactions in La 0.5 Sr 1.5 Ni 1−x Fe x O 4±δ Ruddlesden-Popper oxides

Phase relation and oxygen‐non‐stoichiometry of Perovskite‐like Compound SrCoOx (2.29 2.80)

In the process of oxygen evolution reaction (OER) on perovskite, it is of great significance to accelerate the hindered lattice oxygen oxidation process to promote the slow kinetics of water oxidation. In this paper, a facile surface modification strategy of nanometer-scale iron oxyhydroxide (FeOOH) clusters depositing on the surface of LaNiO3 (LNO) perovskite is reported, and it can obviously promote hydroxyl adsorption and weaken Ni-O bond of LNO. The above relevant evidences are well demonstrated by the experimental results and DFT calculations. The excellent hydroxyl adsorption ability of FeOOH-LaNiO3 (Fe-LNO) can obviously optimize OH- filling barriers to promote lattice oxygen-participated OER (LOER), and the weakened Ni-O bond of LNO perovskite can obviously reduce the reaction barrier of the lattice oxygen participation mechanism (LOM). Based on the above synergistic catalysis effect, the Fe-LNO catalyst exhibits a maximum factor of 5 catalytic activity increases for OER relative to the pristine perovskite and demonstrates the fast reaction kinetics (low Tafel slope of 42 mV dec-1) and superior intrinsic activity (TOFs of ~40 O2 S-1 at 1.60 V vs. RHE).

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Boosting Lattice Oxygen Oxidation of Perovskite to Efficiently Catalyze Oxygen Evolution Reaction by FeOOH Decoration.

Electrocatalysis lies in the center of many clean energy conversion and storage technologies. Developing efficient electrocatalysts to promote the kinetics of the key chemical reactions involved in these processes represents an important research topic. Ruddlesden–Popper perovskites (An+1BnX3n+1), as a layered derivative of the perovskite family (ABX3), are an important class of solid-state materials, and are emerging as high-performing electrocatalysts due to their unique layered structure and rich chemical compositions. In this review, we provide a comprehensive understanding of the structure and properties of Ruddlesden–Popper perovskites in the context of their electrocatalysis applications. We also summarize the recent developments of Ruddlesden–Popper perovskites for catalyzing a breadth of electrochemical reactions at both low and high temperatures. We highlight how Ruddlesden–Popper perovskites can be tailored through a range of design strategies to achieve improved electrocatalysis. Finally, we provide perspectives on future research directions that further expand the electrocatalytic possibilities of Ruddlesden–Popper perovskites.

T. Hashino

Papers

Synthesis of SrNiO3 and related compound, Sr2Ni2O5