Perovskite oxides exhibit potential for use as electrocatalysts in the oxygen evolution reaction (OER). However, their low specific surface area is the main obstacle to realizing a high mass-specific activity that is required to be competitive against the state-of-the-art precious metal–based catalysts. We report the enhanced performance of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) for the OER with intrinsic activity that is significantly higher than that of the benchmark IrO₂, and this result was achieved via fabrication of an amorphous BSCF nanofilm on a surface-oxidized nickel substrate by magnetron sputtering. The surface nickel oxide layer of the Ni substrate and the thickness of the BSCF film were further used to tune the intrinsic OER activity and stability of the BSCF catalyst by optimizing the electronic configuration of the transition metal cations in BSCF via the interaction between the nanofilm and the surface nickel oxide, which enables up to 315-fold enhanced mass-specific activity compared to the crystalline BSCF bulk phase. Moreover, the amorphous BSCF–Ni foam anode coupled with the Pt–Ni foam cathode demonstrated an attractive small overpotential of 0.34 V at 10 mA cm⁻² for water electrolysis, with a BSCF loading as low as 154.8 μg cm⁻².

The creation of crystal phase heterostructures of transition metal chalcogenides, e.g., the 1T/2H heterostructures, has led to the formation of metal/semiconductor junctions with low potential barriers. Very differently, post-transition metal chalcogenides are semiconductors regardless of their phases. Herein, we report, based on experimental and simulation results, that alloying between 1T-SnS₂ and 1T-WS₂ induces a charge redistribution in Sn and W to realize metallic Sn_0.5W_0.5S₂ nanosheets. These nanosheets are epitaxially deposited on surfaces of semiconducting SnS₂ nanoplates to form vertical heterostructures. The ohmic-like contact formed at the Sn_0.5W_0.5S₂/SnS₂ heterointerface affords rapid transport of charge carriers, and allows for the fabrication of fast photodetectors. Such facile charge transfer, combined with a high surface affinity for acetone molecules, further enables their use as highly selective 100 ppb level acetone sensors. Our work suggests that combining compositional and structural control in solution-phase epitaxy holds promises for solution-processible thin-film optoelectronics and sensors.

ZnO@ZIF-8 was synthesized by dry gel conversion (DGC) method, which is a green atom-economical synthesis with very small amount of raw materials. As-synthesized ZnO@ZIF-8 showed potential application as a selective H₂ detector over toluene.

Schematic diagram of the sensing mechanism of the UV-light-assisted PdSe ₂ /InSe heterojunction sensor.