A scalable, binder-free and one-step electric discharge rusting technique is proposed to fabricate high performance Fe–Fe _{1− x} O based coplanar microsupercapacitors.

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 (MoCuO_x) 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.

Due to its low cost, natural abundance, non-toxicity, and high theoretical capacitance, cobalt oxide (CoO) stands as a promising candidate electrode material for supercapacitors. In this study, binder-less molybdenum doped CoO (Mo@CoO) integrated electrodes were one-step fabricated using a simple electric discharge corrosion (EDC) method. This EDC method enables the direct synthesis of Mo@CoO active materials with oxygen vacancy on cobalt substrates, without any pre-made templates, conductive additives, or chemicals. Most importantly, the EDC method enables precise control over the discharge processing parameter of pulse width, which facilitates tailoring the surface morphologies of the as-prepared Mo@CoO active materials. It was found that the fabricated Mo@CoO based symmetric supercapacitor prepared by a pulse width of 24 μs (Mo@CoO-SCs24) achieved a maximum areal capacitance 36.0 mF cm⁻² (0.15 mA cm⁻²), which is 1.83 and 1.97 times higher than that of Mo@CoO-SCs12 and Mo@CoO-SCs36. Moreover, the Mo@CoO-SCs24 devices could be worked at 10 V s⁻¹, which demonstrates their fast charge/discharge characteristic. These results demonstrated the significant potential of the EDC strategy for efficiency fabricating various metal oxide binder-less integrated electrodes for various applications, like supercapacitors, batteries and sensors.

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