One-pot green synthesis of rGO/SnO2 nanocomposites from cellulose and SnCl2 as Lewis acid catalyst

Abstract

The development of sustainable, single-step protocols for fabricating metal oxide-graphene heterostructures remains a critical challenge to overcome the toxicity and complexity of conventional synthesis methods. In this regard, this paper reports a one-pot, cellulose-based hydrothermal route for obtaining reduced graphene oxide/tin dioxide (rGO/SnO₂) nanocomposites. This route exploits tin(II) chloride as a dual-action reducing agent (Lewis acid) and isomerization/dehydration catalyst, inducing the cellulose → glucose → fructose → 5-HMF reaction cascade and the concomitant aromatization to sp² carbon while oxidizing Sn²⁺ to rutile SnO₂. The process yields uniformly dispersed SnO₂ nanocrystallites anchored on few-layer reduced graphene, as confirmed by ATR-FTIR/Raman, XRD, SEM/EDX, and TEM. Raman analysis shows low structural disorder (D/G ≈ 1.72), XRD identifies rutile SnO₂ with an average crystallite size of ∼5.4 nm, and TEM reveals a homogeneous nano-SnO₂ distribution on wrinkled rGO sheets. TGA indicates a Csp²/SnO₂ mass ratio of ∼8, supporting high graphitic content. Density functional theory on a representative Sn₃O₆-rGO model indicates a moderate HOMO–LUMO gap (∼1.30 eV), substantial electrophilicity, and a balanced electrostatic potential, consistent with efficient interfacial electronic communication and adsorption-driven reactivity. By integrating in situ nucleation of ultrasmall SnO₂ with the formation of conductive rGO, the architecture aligns with state-of-the-art SnO₂/graphene hybrids known to accelerate charge transport and redox kinetics for energy storage, catalysis, and gas sensing. The green, single-step workflow avoids external reducing agents and graphitic exfoliation steps, offering a scalable pathway to high-quality SnO₂/rGO heterointerfaces that are broadly applicable to electrochemical, photocatalytic, and room-temperature sensing platforms.