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-C3N4 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-C3N4 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-C3N4 support under the collision of liquid molecules, then two or more nanoparticles attach together via the crystallographic orientation to construct larger ones. Al2O3 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 Al2O3 growth cycles, the photocatalytic hydrogen production of Pt/g-C3N4 coated by Al2O3 increase from 1.14 mmolg−1h−1 to 2.08 mmolg−1h−1 and then decrease to 1.4 mmolg−1h−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.