Electroless deposition and surface analysis of cupro‑nickel coated bio-char for vapor adsorption applications

Abstract

This study comprehensively explores the advanced morphological, thermal, and adsorption properties of cupronickel-coated bio-char, emphasizing its potential for ammonia-based vapor adsorption refrigeration applications. A novel pre-treatment approach has been implemented on bio-char prior to the Electroless process. Through an electro-less deposition process, the bio-char's porous architecture is transformed into a dense nodular morphology, resulting in remarkable enhancements to its thermal and mechanical properties. The coated bio-char demonstrates a substantial 42.9 % increase in thermal conductivity (from 0.203 W/mK to 0.290 W/mK) and a significant 45.9 % rise in specific heat capacity (reaching 1.283 MJ/m³·K). Although the coating process reduces the surface area by 36.5 % (to 483 m²/g) and pore volume by 76.7 % (to 0.176 cc/g), these limitations are effectively counterbalanced by the introduction of catalytic properties, enabling highly efficient chemical adsorption of polar molecules like ammonia. Detailed morphological analyses using FESEM, EDS mapping, and micro-CT scanning revealed a notable reduction in porosity (12.49 %) and enhanced structural integrity, ensuring mechanical durability under harsh and corrosive conditions. Additionally, the cupronickel coating significantly modifies the surface energy, improving the hydrophobicity and optimizing its functionality for ammonia adsorption during refrigeration cycles. BET analysis highlights the coated bio-char's adaptability for chemical adsorption processes, while the un-coated variant excels in physical adsorption, benefiting from its high surface area and pore volume. By seamlessly integrating the enhanced thermal stability, catalytic efficiency, and exceptional mechanical robustness, the cupronickel-coated bio-char emerges as a ground breaking material for sustainable adsorption-based refrigeration systems, offering innovative solutions for critical applications such as cold storage and milk chilling, while advancing energy-efficient cooling technologies.