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Water electrolysis for green hydrogen production is gaining tremendous attention in the quest towards sustainable energy sources. At the heart of water splitting technology are the electrocatalysts, which facilitate the two half-cell reactions, i.e., the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with the latter being the most thermodynamically uphill. Herein, we managed to fabricate Ni 1-x Fe x O microflowers (μFs) with varying % of Fe doping (0 < x < 0.36) via an easy chemical bath deposition (CBD) method. The as-synthesized μFs drop-casted on graphene paper (GP) are then applied as electrocatalysts for OER. Compared to contrast catalysts, the electrocatalyst with x Fe = 0.1 exhibits a lower overpotential of 297 mV at a current density of 10 mA cm−2, Tafel slope of 44 mV dec−1 and unprecedented turnover frequency of 4.6 s−1 at 300 mV. It is believed that this remarkable electrochemical performance mainly stems from the synergistic effects of Ni and Fe species, working in harmony to enhance charge transfer kinetics and intrinsic activity of the catalyst. This work provides a promising avenue for developing cost-effective and highly active electrocatalysts as advanced electrodes for energy related applications. [Display omitted] • Highly active NiFe-based electrocatalysts synthesized by a simple chemical route. • Effect of Fe doping concentration on oxygen evolution reaction of NiO. • Exceptional turnover frequency of Fe-doped NiO electrodes in alkaline conditions. [ABSTRACT FROM AUTHOR]

In this work, we present all-oxide p-n junction core-shell nanowires (NWs) as fast and stable self-powered photodetectors. Hydrothermally grown n-type ZnO NWs were conformal covered by different thicknesses (up to 420 nm) of p-type copper oxide layers through metalorganic chemical vapor deposition (MOCVD). The ZnO NWs exhibit a single crystalline Wurtzite structure, preferentially grown along the [002] direction, and energy gap E g = 3.24 eV. Depending on the deposition temperature, the copper oxide shell exhibits either a crystalline cubic structure of pure Cu 2 O phase (MOCVD at 250 °C) or a cubic structure of Cu 2 O with the presence of CuO phase impurities (MOCVD at 300 °C), with energy gap of 2.48 eV. The electrical measurements indicate the formation of a p-n junction after the deposition of the copper oxide layer. The core-shell photodetectors present a photoresponsivity at 0 V bias voltage up to 7.7 µA/W and time response ≤ 0.09 s, the fastest ever reported for oxide photodetectors in the visible range, and among the fastest including photodetectors with response limited to the UV region. The bare ZnO NWs have slow photoresponsivity, without recovery after the end of photo-stimulation. The fast time response for the core-shell structures is due to the presence of the p-n junctions, which enables fast exciton separation and charge extraction. Additionally, the suitable electronic structure of the ZnO-Cu 2 O heterojunction enables self-powering of the device at 0 V bias voltage. These results represent a significant advancement in the development of low-cost, high efficiency and self-powered photodetectors, highlighting the need of fine tuning the morphology, composition and electronic properties of p-n junctions to maximize device performances. [ABSTRACT FROM AUTHOR]