Phase Engineering of Pd-Te Hexagonal Nanoplates for Enhancing Nitrogen Oxidation

Photocatalytic upgrading of nitrogen (N₂) to value-added chemicals, especially nitrate (NO₃^-) products, is a promising alternative to traditional energy-intensive processes such as ammonia synthesis and ammonia oxidation. Although various strategies have been developed to enhance this reaction, the crystal phase dependence effect in the N₂ oxidation system has still not been explored. In this work, we chose the Pd-Te hexagonal nanoplates with distinct crystalline phases as the research subject and for the first time demonstrated the phase-dependent performance toward solar-driven N₂ oxidation to NO₃^-. Phase tuning of Pd-Te overcomes N₂-to-NO₃^- conversion bottlenecks, with Pd_2.5Te as the most effective catalyst. Under full-spectrum irradiation, the NO₃^- production rate of Pd_2.5Te reaches 372.2 μmol g^-1 h^-1 at room temperature under atmospheric pressure without a sacrificial agent, which is around 4.4 and 6.2 times that of Pd₂₀Te₇ and PdTe, respectively. In situ X-ray photoelectron spectroscopy (XPS), in situ electron paramagnetic resonance (EPR), and in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy show that holes and electrons are generated on the nanoplate surface under photoexcitation, which react with oxygen (O₂) to convert it into hydroxyl radicals (·OH) and superoxide radicals (·O₂), by which N₂ is activated and oxidized to generate NO₃^-. This work highlights the importance of phase engineering for boosting N₂ conversion into NO₃^-.