ICMCTF 2026 Session TS2-ThP: Coatings and Surfaces for Renewable Energy Technology Poster Session

Ammonia plays an important role in modern agriculture and industry, serving as a vital raw material for fertilizers and sustaining societal development. Currently, industrial ammonia production is dominated by the Haber-Bosch process; however, this method is energy-intensive and responsible for significant carbon dioxide emissions. To address this drawback, electrocatalytic nitrate reduction reaction (NO₃^-RR) represents a promising sustainable way toward ammonia synthesis. Thus, the development of high-performance electrocatalysts for NO₃^-RR has been receiving tremendous attention recently. In this study, we have investigated transition metal oxide-based NO₃^-RR electrocatalyst. The electrocatalyst is synthesized using a hydrothermal process followed by thermal annealing. When operated in alkaline electrolyte, the catalyst exhibits a high faradaic efficiency of 83% and a high ammonia yield up to 0.47 mmol h^-1 cm^-2. With its excellent NO₃^-RR performance and cost-effectiveness, the synthesized catalyst is highly promising for sustainable ammonia production.

Transition-metal-oxide functional coatings have emerged as promising candidates for next-generation electrochemical energy storage systems due to their high theoretical capacitance, chemical stability, and tunable ion-transport pathways. In this work, a comparative evaluation of α-MnO₂ and δ-MnO₂ phases is reported, focusing on their performance as active electrode coatings. Four MnO₂ variants were synthesized via hydrothermal processing, yielding two α-type and two δ-type compositions with distinct structural and morphological characteristics. The coatings were deposited onto stainless-steel mesh substrates and characterized by XRD, FT-IR, and SEM, confirming phase purity and the formation of hierarchical nanostructures that directly influence electrolyte accessibility.

Electrochemical testing cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, revealed that δ-MnO₂ exhibited superior behavior, achieving specific capacitances above 300 F g⁻¹ at 0.1 A g⁻¹ and enhanced cycling stability (>90% capacitance retention after 2000 cycles). Nyquist analysis confirmed reduced charge-transfer resistance for δ-MnO₂, attributed to improved interlayer ion diffusion and increased electroactive surface area.

These findings highlight δ-MnO₂ as a high-performance material for supercapacitor applications, and demonstrate its potential integration in scalable metal-mesh-based electrode architectures for energy storage systems.

Keywords: MnO₂ coatings, energy-storage electrodes, hydrothermal synthesis, supercapacitors.