Roshan Mangal Bhattarai

Designing electrode materials that are both sustainable and electrochemically effective is essential for the continued advancement of energy storage systems. Herein, seaweed-derived activated carbon (SWAC) was synthesized from Pyropia yezoensis via a facile activation-functionalization strategy using KOH activating agent. Notably, the optimized SWAC-800 (calcined at 800 ℃) sample exhibited an ultrahigh specific surface area of 4224 m2 g⁻1, with porous structure and intrinsic nitrogen functionalities. SWAC-800 delivers a specific capacitance of 549.7 and 224 F g⁻1 at 1.0 A g⁻1 in three electrode and two electrode system, respectively. The symmetric device delivered a high energy density of 31.1 Wh kg⁻1 with excellent long-term cycling stability over 18,000 cycles. Furthermore, symmetric supercapacitors connected in series successfully powered the commercial LEDs for more than 200 s. Systematic regulation of activation temperature enables precise control over pore evolution, resulting in an ultrahigh surface area and an optimized micro/mesoporous architecture. This proposed green and economically viable approach not only promotes the effective utilization of a marine biomass but also offers a pathway for the development of advanced electrode materials toward sustainable energy storage applications.

Supercapacitors have been studied as a potential complementary technology for rechargeable batteries, fuel cells, and dielectric capacitors.

The traditional lithium‐ion battery (LIB) electrode has reached its limitations in terms of energy density and fast charging capabilities. To enable implementation in electric vehicles and other applications, 3D structuring is a method frequently proposed to allow for performance enhancement due to an increase in electrode surface area. Due to the decrease in lithium ion diffusion pathways, potential for application in thick electrodes exists, allowing further enhancement of energy density. Laser ablation is a promising manufacturing technique for the fabrication of 3D structured electrodes due to its ease of implementation in the existing electrode manufacturing process, as well as its flexibility and precision. This review details the main process parameters of the laser ablation process and their influence on the process efficiency and quality of generated structures. It further summarizes recent progress in finding the optimal electrode structure for both cathode and anode, and discusses the opinions on relative importance of cathode v. anode structuring. Lastly, current progress and challenges for the implementation in the battery manufacturing process are detailed, providing techniques for the upscaling and increase of belt speeds.

This work investigates novel improvements in FeNi‐layered double hydroxide (LDH)/MIL‐88A heterocomposite for sustainable seawater electrolysis through a single‐step dual functionalization process. The Fe/Ni precursor weight ratio is optimized, resulting in the formation of smaller LDH petals and nano‐sized MIL‐88A metal–organic framework, which transforms into clusters of Fe₂O₃ nanospheres within a nitrogen‐functionalized carbon matrix over NiFe₂O₄ nano petals upon calcination. Furthermore, oxygen vacancies, and nitrogen functionalization are attained in a single step by employing thermal ammonia reduction, significantly improving the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities. Particularly the oxygen vacancy and nitrogen functionalization are found to accelerate the O─O coupling step in OER by lowering the activation barrier. Likewise, the dual functionalization promotes destabilizing the hydride intermediates in HER potentially facilitating faster proton‐coupled electron transfer. Hence, the optimized electrode achieves current densities of 200 mA cm⁻² at overpotentials of 350 and 240 mV for OER and HER respectively. The chronopotentiometry stability tests confirms the electrode's durability over 200 h at 20 mA cm⁻² in alkaline seawater electrolyte. The optimized electrode, composed of cost‐effective and environmentally friendly materials, demonstrates robustness in alkaline seawater electrolytes, positioning it as a strong candidate for practical and sustainable water electrolysis applications.

Developing an energy storage electrocatalyst that excels in efficiency, cost-effectiveness, and long-term stability over numerous charge–discharge cycles is paramount for advancing energy storage technologies. In this work, we present a simple and environmentally friendly method to fabricate an asymmetric supercapacitor device (ASCD) as a viable energy storage system. The ASCD features binder-free, oxygen–nitrogen dual functionalized, and sulfurized iron–nickel hydroxysulfide (FNMOS) electrocatalysts, self-grown on nickel foam as a positive electrode, and waste biomass-derived activated carbon (CFAC) as a negative electrode. The FNMOS electrode in a 3-electrode configuration has the highest area-specific capacity of 1.6 mA h cm⁻² at 1 mA cm⁻², and even at a high current density of 10 mA cm⁻², it maintained 0.94 mA h cm⁻². The enhanced electrocatalytic activity is due to the synergistic contribution of the sulfurized NiFe composite along with the meticulous oxygen–nitrogen co-functionalization. Additionally, the ASCD with the FNMOS positive electrode and the CFAC negative electrode achieves maximum energy density (ED) and power density (PD) values of 350 μW h cm⁻² (825 μW per cm² PD) and 7960 μW cm⁻² (200 μW h per cm² ED). Furthermore, the device demonstrated exceptional rate capability by maintaining over 96% of its initial capacity even after 25 000 cycles of charge and discharge. The exceptional stability was further characterized by the ex situ post-mortem analysis of the FNMOS electrode after the stability test. These encouraging electrochemical results, paired with some practical use cases, demonstrate the applicability of FNMOS as a next-generation energy storage material.