Experimental and Theoretical Insights of Anion Regulation in MOF-Derived Ni–Co-Based Nanosheets for Supercapacitors and Anion Exchange Membrane Water Electrolyzers

Abstract

The anionic components have a significant role in regulating the electrochemical properties of mixed transition-metal (MTM)-based materials. However, the relationship between the anionic components and their inherent electrochemical properties in MTM-based materials is still unclear. Herein, we report the anion-dependent supercapacitive and oxygen evolution reaction (OER) properties of in situ grown binary Ni–Co–selenide (Se)/sulfide (S)/phosphide (P) nanosheet arrays (NAs) over nickel foam starting from MOF-derived Ni–Co layered double hydroxide precursors. Among them, the Ni–Co–Se NAs exhibited the best specific capacity (289.6 mA h g–1 at 4 mA cm–2). Furthermore, a hybrid device constructed with Ni–Co–Se NAs delivered an excellent energy density (74 W h kg–1 at 525 W kg–1) and an ultra-high power density (10 832 W kg–1 at 46 W h kg–1) with outstanding durability (∼94%) for 10 000 cycles. Meanwhile, the Ni–Co–Se NAs showed superior electrocatalytic OER outputs with the lowest overpotential (235 mV at 10 mA cm–2) and Tafel slope. In addition, Ni–Co–Se NAs outperformed IrO2 as an anode in an anion exchange membrane water electrolyzer at a high current density (>1.0 A cm–2) and exhibited a stable performance up to 48 h with a 99% Faraday efficiency. Theoretical analyses validate that the Se promotes OH adsorption and improves the electrochemical activity of the Ni–Co–Se through a strong electronic redistribution/hybridization with an active metal center due to its valence 4p and inner 3d orbital participations. This study will provide in-depth knowledge of bifunctional activities in MTM-based materials with different anionic substitutions.

Interconnected CoNi-Se Hollow Flakes through Reduced Graphene Oxide Sheets as a Cathode Material for Hybrid Supercapacitors

“…Moreover, In Figure a, the Co 2p 3/2 states (at 780.8/784.5 eV for Co 3+ /Co 2+ ions, respectively) and Co 2p 1/2 states (at 795.5 and 797.1 eV for Co 3+ and Co 2+ , respectively) are evident, accompanied by broad satellite peaks at 802 eV. This observation confirms the coexistence of Co 3+ and Co 2+ ions within the CoNi-Se/rGO system in addition to the Co o metal peak at 778 eV. , In Figure b, the Ni 2p spectrum unveils distinct peaks at 855.7 and 857.7 eV, characterizing Ni 2p 3/2 and suggesting Ni 2+ and Ni 3+ oxidation states. In the meantime, the photopeaks at 873.2 and 874.7 eV in 2p 1/2 correspond to Ni 2+ and Ni 3+ , respectively.…”

“…Despite these advantages, SCs face limitations, primarily in energy density compared with traditional secondary batteries. This disparity has, to some extent, hindered their widespread commercial utilization. − Electrochemical SC electrodes are classified based on their charge-storage mechanisms and can be broadly grouped into three categories. To begin, electrodes classified as electric double-layer capacitive (EDLC) operate by storing charge through physical adsorption/desorption phenomena taking place on the electrode material’s surface.…”

An effective lithium incorporation strategy to boost the charge-storage capacity of bimetallic metal–organic frameworks with theoretical insights and solid-state lithium-ion capacitors

“…, Bader charge difference upon Li atom adsorption on the NiCo MOF structure (positive and negative signs represent charge gain and loss upon adsorption). 81,82 The NiCo MOF structure receives a significant amount of electrons, 0.888 e for the O–Co–O site (see Fig. 9d), and 0.871 e for the M 2 O 4 center site (see Fig.…”

Two-Dimensional Synergistic Interfacial Orientation on Tin Oxide-Reinforced Cobalt Carbonate Hydroxide Heterostructures for High-Performance Energy Storage

“…A two-dimensional transition metal hydroxides (2D-TMHs)-based aqueous supercapacitor electrodes have been employed in a diverse range of metal cations (Ni, Co, Mn, Fe, Cd, and Cu) to easily access more OH – in aqueous systems . It should be clear that the material properties of TMHs have notable attributes such as simple fabrication techniques, large surface regions, significantly ample electroactive sites, and integration with heterogeneous electrocatalyst supports. − Meanwhile, the emergence of effective morphological architecture with battery-type electrochemical profile has gained recognition for the TMHs electrode, which will enable further advances in the energy density of supercapacitors (SC). − In general, each charge/discharge process can cause transition of at least one phase toward the high/low valence substances, which tends to rise in the charge storage behavior of the battery-type material. Owing to the apparent battery-type charge storage process, these materials have high electrochemical activity with excellent kinetics almost equivalent or even superior to the capacitor-type counterparts. , Furthermore, the choice of the electrode is primarily governed by the energy storage mechanisms and centered on kinetic behaviors endorsement depending on either diffusion-controlled or intercalation-controlled charge storage performance of the electrode materials. , The cobalt hydroxides-based battery-type electrodes have drawn interest owing to their 2D layered structure, rich electroactive sites, multiple oxidation states, and high theoretical capacity. − In view of the environmental convenience, synthesis flexibility, and theoretical capacity, cobalt carbonate hydroxides have spurred interest as high-performance battery-type electrodes.…”