Tailoring Alginate and Graphitic Carbon Nitride Hydrogel Geometries via 3D Printing for Efficient Photocatalytic Solar-Driven Hydrogen Evolution

High Resolution Image Download MS PowerPoint Slide Graphitic carbon nitride (g-CN), a visible-light-active and metal-free photocatalyst, demonstrates great potential but suffers from its practical use in a particulate form. Platinum (Pt)-modified g-CN (Pt@g-CN) particles with a narrow band gap energy of 2.76 eV and higher photocatalytic HER activity up to 20-fold compared to their pristine form were obtained via a daylight-driven photodeposition method onto melamine-based g-CN particles. Improving the practical application, the Pt@g-CN particles were formulated into a 3D-printable hydrogel using alginate as a biobased matrix, resulting in an elastic solid-like ( G ′ > G ″) ink suitable for direct-ink-writing printing. Molecular-level evidence for the stabilizing interactions within the composite investigated by density functional theory (DFT) revealed thermodynamically favorable ternary alginate/Pt@g-CN structures stabilized through cooperative noncovalent hydrogen-bond-like interactions. Exploiting the unique physical properties of alginate/Pt@g-CN composite, having excellent solution uptake capacity of 167% and porous structure that creates a unique hydrated microenvironment and induces internal light scattering in the hydrogel interior, which consequently eases the mass transfer and light absorption and combined with the effect of tailored hydrogel structures that modulate the internal light distribution as confirmed by Monte Carlo photon-transport simulations. The composite with band gap energy of 2.69 eV showed a 3-fold increase in H 2 yield compared to nonimmobilized Pt@g-CN powders and maintained photoredox stability for up to 15 h. This research truly highlighted the advantageous proposed synergistic approach to obtain sustainable, scalable, and practical materials for renewable H 2 generation.