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<p>This work reports a sustainable route for synthesizing a silver nanoparticle/reduced graphene oxide nanocomposite supported on activated carbon (AgNPs/rGO/AC810), using aqueous extract of guarana seed skins as a natural reducing and stabilizing agent. The extract promotes the reduction of Ag⁺ to silver nanoparticles (AgNPs) and graphene oxide (GO) to reduced graphene oxide (rGO), followed by deposition onto commercial activated carbon (AC810). UV–vis spectroscopy revealed the Ag surface plasmon resonance band and provided evidence of GO reduction to rGO, with the GO band at λmax ≈ 235&#xa0;nm disappearing and a broad rGO band appearing at λmax ≈ 398&#xa0;nm. XRD analysis revealed the face-centered cubic structure of metallic Ag with an average crystallite size of 11.39&#xa0;nm. HR-TEM images showed uniformly dispersed spherical AgNPs anchored on rGO sheets and within AC810 pores, with average sizes of ~ 8&#xa0;nm in AgNPs/rGO and ~ 13&#xa0;nm in AgNPs/rGO/AC810. Raman and ATR-FTIR analyses supported the partial restoration of sp² domains, with ID/IG values of 1.20 for GO and 1.10 for AgNPs/rGO, and characteristic carbon functionalities. BET/BJH analysis revealed a high surface area of approximately 600&#xa0;m² g⁻¹ and a predominantly mesoporous structure, favorable for active-site accessibility and mass transport. DLS/zeta potential results indicated colloidal stability under alkaline conditions, with hydrodynamic diameter around 240&#xa0;nm and zeta potential near − 30 to − 35 mV. Electrochemical characterization showed a significant increase in ECSA from 0.003&#xa0;cm² for GCE to 0.177&#xa0;cm² for AgNPs/rGO/AC810/GCE, corresponding to an approximately 59-fold enhancement and a roughness factor increase from 0.03 to 1.77, indicating a high density of accessible active sites. These results indicate that AgNPs/rGO/AC810 is a low-cost and versatile nanocomposite platform for future CO₂RR studies.</p>

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Structural, physical and electrochemical characterization of silver nanoparticles with reduced graphene oxide in activated carbon obtained by a green route

  • 期刊论文

  • 发表日期：

    2025年12月1日

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  • Rodrigo Botinelly Nogueira,
  • Arthur Henrique Azevedo Gonçalves,
  • Carla Ramos Moreira,
  • João Tedim,
  • António Alexandre Cunha Bastos,
  • Fabiana Magalhães Teixeira Mendes,
  • Alexandre Barros Gaspar,
  • Javier Alejandro Carreno Velasco,
  • Dachamir Hotza

摘要

This work reports a sustainable route for synthesizing a silver nanoparticle/reduced graphene oxide nanocomposite supported on activated carbon (AgNPs/rGO/AC810), using aqueous extract of guarana seed skins as a natural reducing and stabilizing agent. The extract promotes the reduction of Ag⁺ to silver nanoparticles (AgNPs) and graphene oxide (GO) to reduced graphene oxide (rGO), followed by deposition onto commercial activated carbon (AC810). UV–vis spectroscopy revealed the Ag surface plasmon resonance band and provided evidence of GO reduction to rGO, with the GO band at λmax ≈ 235 nm disappearing and a broad rGO band appearing at λmax ≈ 398 nm. XRD analysis revealed the face-centered cubic structure of metallic Ag with an average crystallite size of 11.39 nm. HR-TEM images showed uniformly dispersed spherical AgNPs anchored on rGO sheets and within AC810 pores, with average sizes of ~ 8 nm in AgNPs/rGO and ~ 13 nm in AgNPs/rGO/AC810. Raman and ATR-FTIR analyses supported the partial restoration of sp² domains, with ID/IG values of 1.20 for GO and 1.10 for AgNPs/rGO, and characteristic carbon functionalities. BET/BJH analysis revealed a high surface area of approximately 600 m² g⁻¹ and a predominantly mesoporous structure, favorable for active-site accessibility and mass transport. DLS/zeta potential results indicated colloidal stability under alkaline conditions, with hydrodynamic diameter around 240 nm and zeta potential near − 30 to − 35 mV. Electrochemical characterization showed a significant increase in ECSA from 0.003 cm² for GCE to 0.177 cm² for AgNPs/rGO/AC810/GCE, corresponding to an approximately 59-fold enhancement and a roughness factor increase from 0.03 to 1.77, indicating a high density of accessible active sites. These results indicate that AgNPs/rGO/AC810 is a low-cost and versatile nanocomposite platform for future CO₂RR studies.