Light-Induced Dispersion of Pd Single Atoms Provides Steady-State-Stabilized Activity for Photocatalytic H₂...

In recent years, the use of single atoms (SAs) has become increasingly significant in photocatalysis. Particularly, SA noble metals of Pt and Pd can act as highly effective co-catalysts for the hydrogen production reaction. The main challenge in the use of SA catalysts is agglomeration, and most importantly, for photocatalysts, light-induced agglomeration that rapidly degrades the catalytic performance. Here, we show, however, that for Pd SAs on an ideal flat TiO₂ thin-film platform, under a constant, sufficiently high photon flux, a highly dispersed and highly active SA configuration can be maintained, i.e., agglomeration to nanoparticles and activity loss can be prevented. We ascribe this, supported by DFT, to the destabilizing effect of a high hydrogen loading on Pd 2D rafts consisting of few atoms and the high mobility of the Pd-H intermediates. This, in contrast to Pt, provides an energetics that allows to maintain a dispersion-aggregation equilibrium, which results in a steady-state that macroscopically can provide a remarkably high SA-stability during photocatalytic experiments, maintaining the photocatalyst in a state of highest activity.