Morphology Matters: 0D/2D WO3 Nanoparticle‐Ruthenium Oxide Nanosheet Composites for Enhanced Photocatalytic Oxygen Evolution Reaction Rates

Abstract In the field of artificial photosynthesis with semiconductor light harvesters, the default cocatalyst morphologies are isotropic, 0D nanoparticles. Herein, the use of highly anisotropic 2D ruthenium oxide nanosheet (RONS) cocatalysts as an approach to enhance photocatalytic oxygen evolution (OER) rates on commercial WO 3 nanoparticles (0D light harvester) is presented. At optimal cocatalyst loadings and identical photocatalysis conditions, WO 3 impregnated with RONS (RONS/WO 3 ) shows a fivefold increase in normalized photonic efficiency compared to when it is impregnated with conventional ruthenium oxide (rutile) nanoparticles (RONP/WO 3 ). The superior RONS/WO 3 performance is attributed to two special properties of the RONS: i) lower electrochemical water oxidation overpotential for RONS featuring highly active edge sites, and ii) decreased parasitic light absorption on RONS. Evidence is presented that OER photocatalytic performance can be doubled with control of RONS edges and it is shown that compared to WO 3 impregnated with RONP, the advantageous optical properties and geometry of RONS decrease the fraction of light absorbed by the cocatalyst, thus reducing the parasitic light absorption on the RONS/WO 3 composite. Therefore, the results presented in the current study are expected to promote engineering of cocatalyst morphology as a complementary concept to optimize light harvester‐cocatalyst composites for enhanced photocatalytic efficiency.