Establishment of a sustainable energy society has been strong driving force to develop cost-effective and highly active catalysts for energy conversion and storage devices such as metal-air batteries and electrochemical water splitting systems. This is because the oxygen evolution reaction (OER), a vital reaction for the operation, is substantially sluggish even with precious metals-based catalysts. Here, we show for the first time that a hexagonal perovskite, BaNiO3, can be a highly functional catalyst for OER in alkaline media. We demonstrate that the BaNiO3 performs OER activity at least an order of magnitude higher than an IrO2 catalyst. Using integrated density functional theory calculations and experimental validations, we unveil that the underlying mechanism originates from structural transformation from BaNiO3 to BaNi(0.83)O(2.5) (Ba6Ni5O15) over the OER cycling process.

For efficient catalysis and electrocatalysis well‐designed, high‐surface‐area support architectures covered with highly dispersed metal nanoparticles with good catalyst‐support interactions are required. In situ grown Ni nanoparticles on perovskites have been recently reported to enhance catalytic activities in high‐temperature systems such as solid oxide cells (SOCs). However, the micrometer‐scale primary particles prepared by conventional solid‐state reactions have limited surface area and tend to retain much of the active catalytic element within the bulk, limiting efficacy of such exsolution processes in low‐temperature systems. Here, a new, highly efficient, solvothermal route is demonstrated to exsolution from smaller scale primary particles. Furthermore, unlike previous reports of B‐site exsolution, it seems that the metal nanoparticles are exsolved from the A‐site of these perovskites. The catalysts show large active site areas and strong metal‐support interaction (SMSI), leading to ≈26% higher geometric activity (25 times higher mass activity with 1.4 V of Eon‐set) and stability for oxygen‐evolution reaction (OER) with only 0.72 µg base metal contents compared to typical 20 wt% Ni/C and even commercial 20 wt% Ir/C. The findings obtained here demonstrate the potential design and development of heterogeneous catalysts in various low‐temperature electrochemical systems including alkaline fuel cells and metal–air batteries.

First ever transparent bendable secondary zinc-air batteries were fabricated. Transparent stainless-steel mesh was utilized as the current collector for the electrodes due to its reliable mechanical stability and electrical conductivity. After which separate methods were used to apply the active redox species. For the preparation of the anode, zinc was loaded by an electroplating process to the mesh. For the cathode, catalyst ink solution was spray coated with an airbrush for desired dimensions. An alkaline gel electrolyte layer was used for the electrolyte. Microscale domain control of the materials becomes a crucial factor for fabricating transparent batteries. As for the presented cell, anionic exchange polymer layer has been uniquely incorporated on to the cathode mesh as the separator which becomes a key procedure in the fabrication process for obtaining the desired optical properties of the battery. The ionic resin is applied in a fashion where controlled voids exist between the openings of the grid which facilitates light passage while guaranteeing electrical insulation between the electrodes. Further analysis correlates the electrode dimensions to the transparency of the system. Recorded average light transmittance is 48.8% in the visible light region and exhibited a maximum power density of 9.77 mW/cm 2 . The produced battery shows both transparent and flexible properties while maintaining a stable discharge/charge operation.

A hexagonal perovskite BaNiO3 with unusually high-valence nickel(iv) was synthesized under atmospheric and low-temperature conditions by an ethylenediamine-derived wet-chemical route. Secondary phases disappeared with increase in the pH value, and the single-phase BaNiO3 was successfully synthesized at pH 10. The specific surface area was ∼32 m(2) g(-1), which is significantly enhanced compared to the BaNiO3 (0.3 m(2) g(-1)) synthesized by flux-mediated crystal growth. The BaNiO3 was used as an oxygen-evolution reaction (OER) catalyst, and the specific mass activity was ∼5 times higher than that of the BaNiO3 synthesized by flux-mediated crystal growth. As a result, the ethylenediamine-derived sol-gel synthesis could be a simple technique to prepare crystalline compounds such as perovskites and spinels, with unusually high-valence transition metals.