In the present work, we report a sustainable approach to synthesize hybrid materials composed of zinc oxide nanoparticles onto reduced graphene oxide (rGO-ZnO), prepared from the conversion of rice husk ash (RHA) into reduced graphene oxide (rGO) via high-temperature KOH solid dissolution to form a template for posterior Zinc oxide interaction. Two distinct routes for decorating ZnO nanoparticles (NPs) onto the rGO matrix were done, and the hybrid material was tested for applications as supercapacitor electrodes. The synthesis routes denominated post adsorbed, by physical adsorption of pre-synthesized ZnO NPs onto rGO structure, and in situ by generation where the rGO is in contact with <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$Zn^{2+}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>Z</mi> <msup> <mi>n</mi> <mrow> <mn>2</mn> <mo>+</mo> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> ions with a posterior reduction of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$Zn^{2+}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>Z</mi> <msup> <mi>n</mi> <mrow> <mn>2</mn> <mo>+</mo> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> at the surface and calcination for zinc oxide nanoparticles formation. The resulting composites were thoroughly characterized using FTIR, SEM/AFM, BET, XRD, UV–Vis-DRS, and cyclic voltammetry (CV). The in situ route (rGO-ZnO-in) yielded smaller ZnO NPs (10–20 nm) with higher surface area vs the post-adsorption composite. Hybrid compounds were used to construct electrodes and test their capacitance by cyclic voltammetry. The rGO-ZnO-in electrode exhibited significantly enhanced electrochemical performance, showing 38% higher current density and a superior capacitance of 26 <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\mu $</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation>F (at 1 A/g) compared to the rGO electrode 16 <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\mu $</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation>F. These results confirm that the in situ synthesis strategy is highly effective for creating optimal nanostructures that facilitate rapid ion diffusion and efficient charge transfer, with applications in high-performance supercapacitor fabrication.

Green synthesis of nanoparticles ZnO-graphene oxide hybrid from rice husk ash: a comparative study of post-adsorption vs in situ synthesis routes

期刊论文
发表日期：

2026年5月28日

查看全文

Jimmy Castillo,
Elsy Bastidas,
Sinai Ortega,
Maria Rodriguez,
Jose D. Martinez

摘要

In the present work, we report a sustainable approach to synthesize hybrid materials composed of zinc oxide nanoparticles onto reduced graphene oxide (rGO-ZnO), prepared from the conversion of rice husk ash (RHA) into reduced graphene oxide (rGO) via high-temperature KOH solid dissolution to form a template for posterior Zinc oxide interaction. Two distinct routes for decorating ZnO nanoparticles (NPs) onto the rGO matrix were done, and the hybrid material was tested for applications as supercapacitor electrodes. The synthesis routes denominated post adsorbed, by physical adsorption of pre-synthesized ZnO NPs onto rGO structure, and in situ by generation where the rGO is in contact with $Zn^{2+}$ $Z n^{2 +}$ ions with a posterior reduction of $Zn^{2+}$ $Z n^{2 +}$ at the surface and calcination for zinc oxide nanoparticles formation. The resulting composites were thoroughly characterized using FTIR, SEM/AFM, BET, XRD, UV–Vis-DRS, and cyclic voltammetry (CV). The in situ route (rGO-ZnO-in) yielded smaller ZnO NPs (10–20 nm) with higher surface area vs the post-adsorption composite. Hybrid compounds were used to construct electrodes and test their capacitance by cyclic voltammetry. The rGO-ZnO-in electrode exhibited significantly enhanced electrochemical performance, showing 38% higher current density and a superior capacitance of 26 $\mu $ $μ$ F (at 1 A/g) compared to the rGO electrode 16 $\mu $ $μ$ F. These results confirm that the in situ synthesis strategy is highly effective for creating optimal nanostructures that facilitate rapid ion diffusion and efficient charge transfer, with applications in high-performance supercapacitor fabrication.