Exploring the efficient catalytic activity of mixed-phase palladium selenides in oxygen reduction reaction

Abstract

Mixed-phase palladium selenides (PdxSey) were synthesized using a single organometallic precursor, offering precise control over the phase distribution and enabling a comprehensive study of phase-dependent electrocatalytic performance. Rietveld refinement of the X-ray diffraction data supported by inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy analyses revealed a progressive transition from Se-rich (PdSe2) to Se-deficient (Pd34Se11) phases with increasing synthesis temperature. This phase transformation is critical for enhancing the catalytic activity of materials. Among the synthesized catalysts prepared at different synthesis temperatures, PdxSey-1000 synthesized at 1000 °C exhibited exceptional oxygen reduction reaction (ORR) performance, achieving a half-wave potential of 0.931 V and demonstrating remarkable durability, with only a 7 mV shift in half-wave potential after 20,000 accelerated durability tests. The superior catalytic activity and stability of the mixed-phase PdxSey-1000 compounds are attributed to the synergistic interactions between distinct crystalline phases, such as PdSe2, Pd17Se15, Pd4Se, and surface Pd. These interactions modulate electronic structures, fine-tune intermediate binding energies, and facilitate efficient pathway transitions during the ORR process. Theoretical calculations revealed that the coexistence of these phases optimized specific reaction steps, leveraging the unique strengths of each phase to minimize the energy barriers and enhance the overall reaction kinetics. This study highlights the transformative potential of leveraging the synergistic effects in mixed-phase compounds. It demonstrates their potential as high-performance and durable alternatives to traditional electrocatalysts. These findings pave the way for the rational design of multi-phase materials for advanced energy-conversion applications. © 2025 Elsevier B.V.