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Owing to high theoretical specific capacitance of 3560 F g −1 and intrinsic activity towards oxygen evolution reaction (OER), inexpensive Co 3 O 4 is drawing much attention as either a promising pseudocapacitive electrode or OER catalyst. However, restricted to poor conductivity and lack of active sites, Co 3 O 4 usually exhibits limited experimental capacitance and OER activity, barely satisfying high energy density delivering of supercapacitors and low energy input of water-splitting systems. Herein, we report O 2 2- /O - functionalized oxygen-deficient Co 3 O 4 nanorods for supercapacitor and water splitting dual applications. The CoC 2 O 4 ·2H 2 O converted oxygen-deficient Co 3 O 4 nanorods show enhanced electrical conductivity as confirmed by the increased carrier density. The increased number of Co 2+ sites (oxygen vacancies) and CoOOH are believed to contribute to the improvement in faradaic reactions and OER activity. Additionally, surface functionalization by O 2 2- /O - is realized in oxygen-deficient Co 3 O 4 nanorods. On the basis of these merits, the as-synthesized Co 3 O 4 nanorods demonstrate a significantly high specific capacitance of 739 F g −1 and an ultralow overpotential of 275 mV at 10 mA cm −2 for OER with ultralong stability of over 300 h (@ 100 mA cm −2 ). Specifically, an electrolyzer for overall water splitting can be driven by asymmetric supercapacitors with the optimized cobalt oxide as both electrocatalyst and electrode material. [ABSTRACT FROM AUTHOR]

A class of ruthenium-nickel alloy catalysts featured with nanoporous nanowires (NPNWs) were synthesized by a strategy combining rapid solidification with two-step dealloying. RuNi NPNWs exhibit excellent electrocatalytic activity and stability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in which the RuNi-2500 NPNWs catalyst shows an OER overpotential of 327 mV to deliver a current density of 10 mA cm−2 and the RuNi-0 NPNWs catalyst requires the overpotential of 69 mV at 10 mA cm−2 showing the best HER activity in alkaline media. Moreover, the RuNi-1500 NPNWs catalyst was used as the bifunctional electrocatalyst in a two-electrode alkaline electrolyzer for water splitting, which exhibits a low cell voltage of 1.553 V and a long-term stability of 24 h at 10 mA cm−2, demonstrating that the RuNi NPNWs catalysts can be considered as promising bifunctional alkaline electrocatalysts. A class of ruthenium-nickel alloy catalysts featured with nanoporous nanowires (NPNWs) was synthesized by a strategy combined rapid solidification with two-step dealloying, in which the total cell voltage of RuNi-1500 NPNWs electrolyzer for water splitting is 1.553 V to deliver a current density of 10 mA cm−2. [Display omitted] • A two-step dealloying strategy was used to prepare RuNi catalysts. • RuNi catalysts exhibit a unique nanoporous nanowires (NPNWs) morphology. • RuNi NPNWs catalysts show excellent electrocatalytic performance for OER and HER. • RuNi NPNWs catalysts can be used as bifunctional catalysts for water splitting. [ABSTRACT FROM AUTHOR]

The synthesis of cost-effective and high-performance electrocatalysts for water splitting is the main challenge in electrochemical hydrogen production. In this study, we adopted a high throughput method to prepare bi-metallic catalysts for oxygen/hydrogen evolution reactions (OER/HER). A series of Ni–Mo alloy electrocatalysts with tunable compositions were prepared by a simple co-sputtering method. Due to the synergistic effect between Ni and Mo, the intrinsic electrocatalytic activity of the Ni–Mo alloy electrocatalysts is improved, resulting in excellent HER and OER performances. The Ni 90 Mo 10 electrocatalyst shows the best HER performance, with an extremely low overpotential of 58 mV at 10 mA cm−2, while the Ni 40 Mo 60 electrocatalyst shows an overpotential of 258 mV at 10 mA cm−2 in OER. More significantly, the assembled Ni 40 Mo 60 //Ni 90 Mo 10 electrolyzer only needs a cell voltage of 1.57 V to reach 10 mA cm−2 for overall water splitting. [Display omitted] • A high throughput method was used to prepare Ni–Mo alloy catalysts. • Ni–Mo alloy catalysts exhibit remarkable activity and stability for HER and OER. • The Ni–Mo alloy acts as a bifunctional catalyst for overall water splitting. • The synergistic effect between Ni and Mo leads to the excellent performances. [ABSTRACT FROM AUTHOR]

Exploring highly efficient and robust electrocatalysts to replace the noble metal-based electrocatalysts for alkaline oxygen evolution reaction (OER) is vital and challenging for the conversion of renewable energy. Herein, a novel element incorporation strategy is proposed to synthesize the multi-metallic selenide of (Ni,Fe,Co)Se 2 nanosheets anchored on a stainless steel mesh substrate (NiFeCoSe/SSM). The multi-metallic hybrid film (NiFeCo/SSM) obtained by a co-sputtering method is converted to the (Ni,Fe,Co)Se 2 nanosheets through an alloying-dealloying-selenization process, in which Co and Fe atoms replace part of Ni atoms in the NiSe 2 lattice. The as-obtained NiFeCoSe/SSM displays efficient OER performances in alkaline solutions with an overpotential of 228 mV at 20 mA cm−2 (268 mV at 50 mA cm−2), and a small Tafel slope of 69.8 mV dec−1 in 1.0 M KOH. Furthermore, the NiFeCoSe/SSM electrode demonstrates a remarkable catalytic stability as long as 24.0 h, and its initial nanosheet structure can be well retained after the durability test. Such excellent OER performances of NiFeCoSe/SSM can be attributed to the unique nanosheet structure and the optimized electronic structure due to the synergistic effect among different metallic elements. • A novel element incorporation strategy is proposed to obtain multi-metallic selenide. • Co and Fe atoms replace part of Ni atoms in the NiSe 2 lattice. • The NiFeCoSe/SSM displays efficient OER performances in alkaline solution. • Synergistic effect among metallic elements causes optimized electronic structure. [ABSTRACT FROM AUTHOR]