Carbon nitride immobilized on a reusable 3D-printed support for sustainable visible-light-driven ammonia synthesis

The significant carbon footprint and energy demand of the photocatalytic ammonia system necessitates high catalytic activity, efficient catalyst recovery, and reuse under mild conditions. In this work, we demonstrate efficient visible-light-driven ammonia synthesis using metal-free thermally exfoliated carbon nitride (GCN-T) immobilized on a 3D-printed support (GCN-T/3D). Under visible-LED irradiation (435 nm) and mild heterogeneous reaction conditions, this sustainable, environmentally friendly photocatalyst facilitates improved nitrogen (N₂) activation, emphasizing its potential for effective recovery and reuse in ammonia production. The GCN-T photocatalyst-based process generated 334 µmol.g_cat^-1 h^- 1 ammonium (NH₄⁺) solution when glycerol was used as a hole scavenger, which is approximately three times higher than the rates reported for other GCN-based catalysts. FTIR-ATR, photoluminescence, photoelectrochemical, and UV-Vis DRS analyses were conducted to characterize the prepared catalysts. BET analysis showed that applying a second thermal treatment to GCN material increased the pore volume, thereby improving N₂ adsorption across the catalyst surface and photogenerated carrier separation. Remarkably, the 3D structure with the immobilized catalyst increased the rate of NH₄⁺ generation and enabled at least 4 reutilization runs without loss of activity. An apparent quantum efficiency of 0.020% was obtained using the immobilized catalyst. The study also examined the effect of various scavengers on the NH₄⁺ generation rate. Additionally, experiments using different water matrices, including seawater, yielded moderate results within one hour, highlighting the real-world potential for sustainable ammonia production. This research introduces a photocatalytic approach that combines a 2D metal-free optical semiconductor immobilized over a reusable 3D-printed structure for decentralized, low-carbon ammonia synthesis.