Non Thermal‐Driven Photocatalytic Ammonia Decomposition at Near‐Room Temperature on a Plasmonic Nanocone Array

The efficient and sustainable production of hydrogen is crucial for the transition to a clean energy future. Ammonia (NH 3 ) is an attractive hydrogen carrier due to its high energy density and safe storage properties. However, conventional ammonia decomposition requires high temperatures, making the process energy‐intensive and costly. Here, a plasmon‐driven photocatalytic approach is presented for ammonia cracking at near‐room temperature, utilizing a plasmonic antenna‐reactor system made by a sharp tip anodic alumina oxide (AAO) array coated with a plasmonic Au film (antenna), decorated with Cu nanoparticles (reactors). This nanostructured catalyst harnesses surface plasmon resonances (SPRs) and generates hot carriers under visible light illumination, significantly enhancing the reaction efficiency. The best AAO@Au@Cu configuration exhibited a hydrogen evolution rate of 227 µmol h −1 g Cu −1 under 1 Sun irradiation at 35 °C. The enhanced activity is due to plasmonic non thermal effects, with the highest catalytic activity observed at 565 nm, corresponding to the SPR mode of the nanostructure. Mechanistic insights, supported by XPS, TOF‐SIMS, and spin‐polarized density functional theory calculations, suggested a multi‐step NH 3 decomposition pathway involving NH 2 NH 2 (hydrazine) and NH‐NH intermediates. This study highlights the potential of plasmonic nanomaterials in revolutionizing low‐temperature NH 3 decomposition, paving the way for sustainable hydrogen production at solar intensities.