Phosphorus-Doped Nickel Oxide Micro-Supercapacitor: Unleashing the Power of Energy Storage for Miniaturized Electronic Devices

Synergistic Surface Reconstruction and Interface Engineering in Bimetallic Selenides: Advancing Renewable Energy Storage and Oxygen Evolution

Designing a bimetallic selenide-based heterostructure that possesses high catalytic efficiency, high capacity, and rate capability remains challenging due to constraints imposed by slow reaction kinetics, inadequate electrode utilization, and significant volume deformation. In this study, we successfully engineer a heterostructure comprising carbon nanotubes intertwined with sea urchin-like Bi2Se3@NiSe2 nanostructures having high electronic conductivity, high specific capacity, sufficiently exposed active sites, and favorable charge carrier migration. The interface engineering of the multilevel Bi2Se3@NiSe2 nanostructure on the carbon nanotube (CNT) framework synergistically reduces energetic barriers and accelerates oxygen evolution kinetics as well as promotes faster Faradaic reactions to enhance charge storage. As a consequence, the as-designed flexible supercapacitor device (Bi2Se3@NiSe2-CNT/CTs//AC-CNT/CTs) attains a peak energy density of 75.93 Wh kg-1 and a maximum power density of 15.12 kW kg-1, demonstrating remarkable durability (94.35% capacitance retention) after 40k cycles. The higher density of states near the Fermi level in the Bi2Se3@NiSe2 hybrid enhances electronic conductivity and charge carrier mobility, coupled with efficient OH- adsorption (ΔEa = -4.352 eV@Bi site, ΔEa = -4.932 eV@Ni site), thereby trapping more electrolyte ions and promoting faster redox reactions. Additionally, the induced electronic interactions between core selenides and surface-generated thin layers of hydroxide/oxide synergistically accelerate the reaction kinetics in terms of a lower overpotential (199 mV@20 mA cm-2), a lower Tafel slope (59.2 mV dec-1), and a higher electrochemical surface area (1460.0 cm2) toward oxygen evolution. The proposed study on the construction of dual redox-active site heterostructures is expected to create avenues for advancing renewable energy systems.

Design and Fabrication of MoCuOx Bimetallic Oxide Electrodes for High-Performance Micro-Supercapacitor by Electro-Spark Machining

Transition metal oxides, distinguished by their high theoretical specific capacitance values, inexpensive cost, and low toxicity, have been extensively utilized as electrode materials for high-performance supercapacitors. Nevertheless, their conductivity is generally insufficient to facilitate rapid electron transport at high rates. Therefore, research on bimetallic oxide electrode materials has become a hot spot, especially in the field of micro-supercapacitors (MSC). Hence, this study presents the preparation of bimetallic oxide electrode materials via electro-spark machining (EM), which is efficient, convenient, green and non-polluting, as well as customizable. The fabricated copper-molybdenum bimetallic oxide (MoCuOx) device showed good electrochemical performance under the electrode system. It provided a high areal capacity of 50.2 mF cm-2 (scan rate: 2 mV s-1) with outstanding cycling retention of 94.9% even after 2000 cycles. This work opens a new window for fabricating bimetallic oxide materials in an efficient, environmental and customizable way for various electronics applications.

On-Chip Micro-Supercapacitor with High Areal Energy Density Based on Dielectrophoretic Assembly of Nanoporous Metal Microwire Electrodes

Advances in the Internet of Things (IoT) technology have driven the demand for miniaturized electronic devices, prompting research on small-scale energy-storage systems. Micro-supercapacitors (MSCs) stand out in this regard because of their compact size, high power density, high charge-discharge rate, and extended cycle life. However, their limited energy density impedes commercialization. To resolve this issue, a simple and innovative approach is reported herein for fabricating highly efficient on-chip MSCs integrated with nanoporous metal microwires formed by dielectrophoresis (DEP)-driven gold nanoparticle (AuNP) assembly. Placing a water-based AuNP suspension onto interdigitated electrodes and applying an alternating voltage induces in-plane porous microwire formation in the electrode gap. The DEP-induced AuNP assembly and the gold microwire (AuMW) growth rate can be adjusted by controlling the applied alternating voltage and frequency. The microwire-integrated MSC (AuMW-MSC) electrically outperforms its unmodified counterpart and exhibits a 30% larger electrode area, along with 72% and 78% higher specific and areal capacitances, respectively, than a microwire-free MSC. Additionally, AuMW-MSC achieves maximum energy and power densities of 3.33 µWh cm-2 and 2629 µW cm-2, respectively, with a gel electrolyte. These findings can help upgrade MSCs to function as potent energy-storage devices for small electronics.