A Facile Synthesis of Size-Controllable IrO2 and RuO2 Nanoparticles for the Oxygen Evolution Reaction

The efficiency of the water electrolysis process is restricted by the sluggish kinetics of the oxygen evolution reaction (OER). Developing efficient catalysts and their synthesis methods is highly desired to improve the kinetics of the OER and therefore the overall efficiency of the water electrolysis. In this report, we present a facile wet-chemical method for synthesizing IrO2 and RuO2 nanoparticles (NPs) for the OER. The nanoparticles were synthesized by reducing metal chlorides in ethylene glycol in the presence of polyvinylpyrrolidone, followed by annealing in air. The particle size was controlled by adjusting the annealing temperature. The activity of IrO2 and RuO2 NPs supported on carbon black was investigated by cyclic voltammetry (CV) in alkaline (0.1 M KOH) electrolyte. As-synthesized IrO2 and RuO2 NPs showed high OER activity. The IrO2 NPs exhibited a specific activity of up to 3.5 (±1.6) μA/cm2oxide at 1.53 V (vs. RHE), while the RuO2 NPs achieved a value of 124.2 (±8) μA/cm2oxide. Moreover, RuO2 NPs showed a mass activity for OER, up to 102.6 (±10.5) A/goxide at 1.53 V (vs. RHE), which represents the highest value reported in the literature to date.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore

Nanoscale Effects in Water Splitting Photocatalysis.

From a conceptual standpoint, the water photoelectrolysis reaction is the simplest way to convert solar energy into fuel. It is widely believed that nanostructured photocatalysts can improve the efficiency of the process and lower the costs. Indeed, nanostructured light absorbers have several advantages over traditional materials. This includes shorter charge transport pathways and larger redox active surface areas. It is also possible to adjust the energetics of small particles via the quantum size effect or with adsorbed ions. At the same time, nanostructured absorbers have significant disadvantages over conventional ones. The larger surface area promotes defect recombination and reduces the photovoltage that can be drawn from the absorber. The smaller size of the particles also makes electron-hole separation more difficult to achieve. This chapter discusses these issues using selected examples from the literature and from the laboratory of the author