Synthesis of Na-stabilized nonporous t-ZrO₂ supports and Pt/t-ZrO₂ catalysts and application to water-gas-shift reaction

t-ZrO₂, synthesized under hydrothermal treatment conditions at 150 °C for 20 h using NaOH as the mineralizer, was phase stable up to 600 °C in air. The t-ZrO₂ calcined at 600 °C (denoted as Z600) were nonporous spherical nanocrystallites with an average size of ∼12 nm and a surface area of ∼55 m²/g, which exhibited hydrothermal stability in a wide range of pH environments from acidic to basic conditions at 200 °C for 20 h. Monodispersed platinum nanoparticles ∼1.5 ± 0.3 nm were obtained on the Z600 supported Pt/t-ZrO₂ catalyst by the Pt atomic layer deposition (ALD) method. Na ions were found to play a crucial role in the formation of the stable t-ZrO₂ by incorporating into the internal crystal structure of ZrO₂ during the hydrothermal synthesis. The rate of water-gas-shift (WGS) reaction per mole of surface Pt on the Pt/Z600 catalyst was about five times higher compared to the catalysts prepared on commercial nonporous ZrO₂. The incorporation of Na into the t-ZrO₂ structure had a synergistic effect: stabilizing ZrO ₂ in the tetragonal phase and promoting the WGS reaction.