Characterization of Ruthenium Oxide Nanocluster as a Cocatalyst with (Ga1-xZnx)(N1-xOx) for Photocatalytic Overall Water Splitting

Abstract

The formation and structural characteristics of Ru species applied as a cocatalyst on (Ga_1-xZn_x)(N_1-xO_x) are examined by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. RuO₂ is an effective cocatalyst that enhances the activity of (Ga_1-xZn_x)(N_1-xO_x) for overall water splitting under visible-light irradiation. The highest photocatalytic activity is obtained for a sample loaded with 5.0 wt % RuO₂ from an Ru₃(CO)₁₂ precursor followed by calcination at 623 K. Calcination is shown to cause the decomposition of initial Ru₃(CO)₁₂ on the (Ga_1-xZn_x)(N_1-xO_x) surface (373 K) to form Ru(IV) species (423 K). Amorphous RuO₂ nanoclusters are then formed by an agglomeration of finer particles (523 K), and the nanoclusters finally crystallize (623 K) to provide the highest catalytic activity. The enhancement of catalytic activity by Ru loading from Ru₃(CO)₁₂ is thus shown to be dependent on the formation of crystalline RuO₂ nanoparticles with optimal size and coverage.