Near-infrared driven photocatalytic hydrogen production from ammonia borane hydrolysis using heterostructure-upconverted nanoparticles†

Abstract

This study presents a novel approach to hydrogen evolution through ammonia borane dehydrogenation, utilizing the unique properties of upconverted nanoparticles (UCNPs) and safe, abundant near-infrared (NIR) light. By converting low-energy 980 nm NIR photons into high-energy visible photons, UCNPs offer a significant enhancement in catalytic activity. The fabrication of polystyrene-incorporated UCNPs (PS@UCNPs) prevents catalyst agglomeration and breakage, resulting in a 35-fold increase in activity compared to bare UCNPs. This increase is due to the high-energy emitted photons providing sufficient energy for hydrogen evolution, thereby reducing catalyst costs and eliminating the need for intermediate catalysts. The study also explores platinum-coated UCNPs (Pt@UCNPs), which increase photon absorption by platinum nanoparticles, significantly boosting photocatalytic performance. Pt@UCNPs demonstrated 25 times higher activity than PS@UCNPs, attributed to the unique properties of Pt nanoparticles. The activation energies for PS@UCNPs and Pt@UCNPs were 27.5 kJ mol⁻¹ and 48.8 kJ mol⁻¹, respectively, highlighting the synergistic effect of UCNPs utilizing NIR light and Pt utilizing visible light. Reaction kinetics indicated that hydrogen evolution rates increased with both catalyst and ammonia borane concentrations under NIR light. Recyclability tests confirmed the superior stability and durability of PS@UCNPs over Pt@UCNPs, with consistent hydrogen evolution rates across five cycles and minimal degradation. These findings position PS@UCNPs as a robust catalyst system with significant potential for long-term applications, contributing to the broader field of photochemical catalysis and inspiring further innovations in renewable energy systems. As materials and technologies continue to evolve, NIR-activated photocatalytic processes are expected to play a crucial role in the transition to a sustainable energy future, significantly impacting renewable energy and green chemistry.