New Delhi: Indian researchers have developed a photo-rechargeable supercapacitor that can both harvest and store solar energy within a single integrated device, marking a significant advancement in self-charging energy storage technology.
The innovative photo-rechargeable supercapacitor, also referred to as a photo-capacitor, has been developed by scientists at the Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru – an autonomous institute under the Department of Science and Technology (DST), Government of India.
The device seamlessly combines sunlight conversion and energy storage, eliminating the need for separate solar panels and storage units.
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Photo-Rechargeable Supercapacitor Simplifies Solar Energy Storage Architecture
Conventional solar energy systems typically rely on two independent components – solar panels for energy harvesting and batteries or supercapacitors for storage.
These hybrid systems require additional power management electronics to regulate mismatches in voltage and current, increasing system complexity, cost, energy losses, and physical footprint.
Such challenges are particularly restrictive for miniaturised, portable, and autonomous devices.
The newly developed photo-rechargeable supercapacitor integrates both functions into a single architecture, enabling direct conversion of sunlight into stored electrical energy.
This integration significantly simplifies system design while minimising energy loss during conversion and storage.
Nanowire-Based Design Enhances Photo-Charging Performance
Under the guidance of Dr Kavita Pandey, the research team utilised binder-free nickel-cobalt oxide (NiCo₂O₄) nanowires grown uniformly on nickel foam through an in situ hydrothermal process.
These nanowires, measuring only a few nanometres in diameter and several micrometres in length, form a highly porous and conductive three-dimensional network.
This unique structure enables efficient sunlight absorption while simultaneously storing electrical charge, allowing the material to function as both a solar energy harvester and a supercapacitor electrode.
Photo-Rechargeable Supercapacitor Shows High Capacitance and Stability
Performance testing revealed that the NiCo₂O₄ electrode exhibited a 54% increase in capacitance under illumination, rising from 570 to 880 mF cm⁻² at a current density of 15 mA cm⁻².
The enhancement was attributed to efficient generation and transport of light-induced charge carriers within the nanowire network.
The electrode also demonstrated long-term durability, retaining 85% of its original capacity even after 10,000 charge–discharge cycles, highlighting its suitability for practical applications.
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Device Demonstrates Real-World Applicability Under Varying Light Conditions
To assess real-world performance, researchers fabricated an asymmetric photo-supercapacitor using activated carbon as the negative electrode and NiCo₂O₄ nanowires as the positive electrode.
The device delivered a stable output voltage of 1.2 volts and maintained 88% capacitance retention after 1,000 photo-charging cycles.
The photo-rechargeable supercapacitor operated efficiently across a wide range of illumination conditions, from low indoor lighting to intense two-sun intensity, indicating strong resilience to both mechanical and electrochemical stress.
Theoretical Insights Support Experimental Findings
Alongside experimental validation, theoretical studies were conducted to understand the material’s exceptional performance.
The analysis revealed that nickel substitution in the cobalt oxide framework narrows the band gap to approximately 1.67 eV and induces half-metallic behaviour.
This dual electronic property – semiconducting for one electron spin and metallic for the other – facilitates faster charge transport and higher electrical conductivity, making it particularly suitable for photo-assisted charge storage applications.
Towards Smart, Self-Charging Energy Storage Systems
By integrating sunlight harvesting and energy storage into a single platform, the research introduces self-charging power systems capable of operating in remote or off-grid environments.
The study demonstrates how nanostructured materials can be optimised for light-responsive energy storage through a combination of experimental and theoretical approaches.
The findings, published in Sustainable Energy & Fuels, a journal of the Royal Society of Chemistry, introduce a new class of smart, photo-rechargeable energy storage devices and represent a notable development in renewable energy storage research.
