Architectural Control of TiO ₂ -GO Hybrids via Graphene Oxide Concentration: Balancing Adsorption and Photocatalysis

Efficient water remediation by titanium dioxidegraphene oxide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{TiO}_{2}-\text{GO})$</tex> nanohybrids is governed by their nanoscale architecture, which controls both adsorption and photocatalytic behaviors. In this study, the influence of GO concentration on the structural and functional properties of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TiO}_{2}$</tex>-GO hybrids was systematically examined. Hybrids containing 2, 5, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10 \text{wt}. \%$</tex> GO were synthesized through a sonicationassisted assembly method. A progressive morphological transition was revealed by high-resolution transmission electron microscopy: partial core-shell structures at 2 wt.%, uniform encapsulation at 5 wt. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\%$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TiO}_{2}$</tex> particles entrapped within extensive GO agglomerates at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10 \text{wt}. \%$</tex>. As a result of these transitions, a clear trade-off between adsorption and photocatalysis was observed. Methylene blue adsorption was enhanced monotonically with increasing GO content, whereas photocatalytic activity was maximized at 2 wt.% GO and subsequently diminished at higher loadings. This contrasting behavior was attributed to competing mechanisms, in which increased surface area promoted adsorption while excessive GO induced light shielding, diffusion barriers, and accelerated charge recombination. It is therefore demonstrated that optimal performance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{TiO}_{2}-\text{GO}$</tex> nanohybrids is achieved not by maximizing GO content, but by engineering a finely tuned architecture that enables a synergistic balance between adsorption and photocatalytic efficiency.