Among various efficient electrocatalysts for water splitting, CoFe and NiFe-based oxides/hydroxides are typically promising candidates thanks to their extraordinary activities towards oxygen evolution reaction (OER). However, the endeavor to advance their performance towards overall water splitting has been largely impeded by the limited activities for hydrogen evolution reaction (HER). Herein, we present a CoFeNi ternary metal-based oxide (CoFeNi-O) with impressive hierarchical bimodal channel nanostructures, which was synthesized via a facile one-step dealloying strategy. The oxide shows superior catalytic activities towards both HER and OER in alkaline solution due to the alloying effect and the intrinsic hierarchical porous structure. CoFeNi-O loaded on glass carbon electrodes only requires the overpotentials as low as 230 and 278 mV to achieve the OER current densities of 10 and 100 mA·cm^-2, respectively. In particular, extremely low overpotentials of 200 and 57.9 mV are sufficient enough for Ni foam-supported CoFeNi-O to drive the current density of 10 mA·cm^-2 towards OER and HER respectively, which is comparable with or even better than the already-developed state-of-the-art non-noble metal oxide based catalysts. Benefiting from the bifunctionalities of CoFeNi-O, an alkaline electrolyzer constructed by the Ni foam-supported CoFeNi-O electrodes as both the anode and the cathode can deliver a current density of 10 mA·cm^-2 at a fairly low cell-voltage of 1.558 V. In view of its electrocatalytic merits together with the facile and cost-effective dealloying route, CoFeNi-O is envisioned as a promising catalyst for future production of sustainable energy resources.

Transition-metal dichalcogenides (TMDs) exhibit immense potential as lithium/ sodium-ion electrode materials owing to their sandwich-like layered structures. To optimize their lithium/sodium-storage performance, two issues should be addressed: fundamentally understanding the chemical reaction occurring in TMD electrodes and developing novel TMDs. In this study, WSe₂ hexagonal nanoplates were synthesized as lithium/sodium-ion battery (LIB/SIB) electrode materials. For LIBs, the WSe₂-nanoplate electrodes achieved a stable reversible capacity and a high rate capability, as well as an ultralong cycle life of up to 1,500 cycles at 1,000 mA·g^–1. Most importantly, in situ Raman spectroscopy, ex situ X-ray diffraction (XRD), transmission electron microscopy, and electrochemical impedance spectroscopy measurements performed during the discharge–charge process clearly verified the reversible conversion mechanism, which can be summarized as follows: WSe₂ + 4Li⁺ + 4e^– ↔ W + 2Li₂Se. The WSe₂ nanoplates also exhibited excellent cycling performance and a high rate capability as SIB electrodes. Ex situ XRD and Raman spectroscopy results demonstrate that WSe₂ reacted with Na⁺ more easily and thoroughly than with Li⁺ and converted to Na₂Se and tungsten in the 1^st sodiated state. The subsequent charging reaction can be expressed as Na₂Se → Se + 2Na⁺ + 2e^–, which differs from the traditional conversion mechanism for LIBs. To our knowledge, this is the first systematic exploration of the lithium/sodium-storage performance of WSe₂ and the mechanism involved.