Agglomeration of Pt nanoparticles on the g-C3N4 surface dominated by oriented attachment mechanism and way of inhibition

Abstract

0.3 mol% platinum loaded g-C _3 N _4 sample was prepared by photoreduction method to study the long-term stability of photocatalysts. For the first time, we have discovered the oriented attachment (OA) mechanism growth of Pt nanoparticles on g-C _3 N _4 solid surface, which is completely different from Ostwald ripening (OR) or particle migration and coalescence (PMC) that previously reported. The Pt nanoparticles perform Brownian motion on the surface of g-C _3 N _4 support under the collision of liquid molecules, then two or more nanoparticles attach together via the crystallographic orientation to construct larger ones. Al _2 O _3 film prepared by atomic layer depositon was introduced to inhibit the Brownian motion of Pt nanoparticles. It is found that as the increase of the Al _2 O _3 growth cycles, the photocatalytic hydrogen production of Pt/g-C _3 N _4 coated by Al _2 O _3 increase from 1.14 mmolg ^−1 h ^−1 to 2.08 mmolg ^−1 h ^−1 and then decrease to 1.4 mmolg ^−1 h ^−1 , and the apparent quantum efficiency (QE) also increase from 1.2% to 2.1% and then decrease to 1.4%. Meanwhile, the long-term stability of photocatalyst always increases. This work has revealed new pathway of photocatalytic nanoparticle growth on solid surface and proposed the method to prevent it.

Keywords

• Oriented attachment
• Agglomeration
• g-C3N4
• photocatalytic hydrogen evolution
• ALD