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[Display omitted] • Ru-doped SrFe 1-x Ru x O 3-δ perovskite oxides were successfully fabricated through a modified sol–gel method. • The SrFe 0.7 Ru 0.3 O 3-δ exhibits significantly enhanced bifunctional electrocatalytic activities for HER and OER in alkaline electrolytes. • The DFT studies demonstrate Ru doping optimizes the electronic structure of SrFe 0.7 Ru 0.3 O 3-δ and thus improves the charge transfer efficiency. • An electrolyzer with SFR30 as both the anode and cathode catalysts requires only a cell voltage of 1.58 V vs. RHE to drive a current density of 10 mA cm−2 in an alkaline medium. Recently, perovskite oxides have acquired a rapidly growing research interest in energy storage and conversion systems, especially the electrolysis of water. Rational doping is an extremely effective strategy to enhance the hydrogen evolution reaction/oxygen evolution reaction (HER/OER) of the perovskite oxides. Herein, a series of novel bi-functional electrocatalysts were synthesized by doping Ru in SrFeO 3-δ perovskite oxide (SrFe 1-x Ru x O 3-δ , x = 0, 0.15, 0.30, 0.45) which exhibit remarkable enhancements of HER/OER activities and long-term stabilities in the alkaline solution (1.0 M KOH). Among them, SrFe 0.7 Ru 0.3 O 3-δ (SFR30) shows the best electrocatalytic activities for overall water splitting, exhibiting low overpotentials for HER (∼41 mV) and OER (∼334 mV) at −10 and 10 mA cm−2, respectively, generating current densities of 10 mA cm−2 in alkaline electrolytic cell using the potential of 1.58 V. In addition, the SFR30 electrocatalyst exhibits remarkable stability which can be operated continuously for 96 h without significant delay. Density functional theory (DFT) calculations indicate that Ru doping can effectively modulate the adsorption of intermediates on the active sites to achieve excellent electrocatalytic performance. Many new prospects have been opened for the development of bi-functional electrocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres are synthesized via a simple two-step hydrothermal method as the positive electrode. • The porous biomass-derived carbon with the honeycomb structure is obtained from pine petals as the negative electrode. • Hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres and the porous biomass-derived carbon possess a high specific capacity. • The hybrid supercapacitor exhibits excellent energy and power density. The high-performance hybrid supercapacitor (HSC) with high power capability and stable cyclability is intensively pursued as a next-generation energy storage device. Here, a kind of hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres, consisting of subunits of NiC 2 O 4 nanorods and Ni(OH) 2 nanospheres, are synthesized via a two-step hydrothermal method. The hierarchical NiC 2 O 4 /Ni(OH) 2 nanosphere positive electrode, benefiting from the synergistic effect of unique hierarchical structure and built-in electric fields, significantly boosting electron transmission capability and accelerating the ion/electron transfer rate, delivers an excellent specific capacity of 668 C g−1 at 1 A g−1. In addition, the porous biomass-derived carbon (PBC) with the honeycomb structure from pine petals as the negative electrode shows a remarkable electrochemical performance, exhibiting a specific capacitance of 249.7 F g−1 at 1 A g−1. As such, an assembled HSC of NiC 2 O 4 /Ni(OH) 2 ||PBC based on hierarchical NiC 2 O 4 /Ni(OH) 2 nanospheres positive electrode and PBC negative electrode display a conspicuous energy density of 31.07 Wh kg−1, and a power density of 833.47 W kg−1 at a maximum potential window of 1.7 V. This innovative hierarchical engineering of double nickel-based composites with bio-carbon provides an advanced enlightenment for high-performance HSCs. [ABSTRACT FROM AUTHOR]