Facet-Controlled Growth of Molybdenum Phosphide Single Crystals for Efficient Hydrogen Peroxide Synthesis

Transition metal phosphides (TMPs) stand out for their excellent catalytic activity, driven by metal‒phosphorus bonding that promotes electron donation, which makes them ideal for electrocatalysis applications. However, the synthesis of single-crystal TMP, which is essential for elucidating intrinsic properties, remains challenging owing to the lack of efficient methods, low yields, and lengthy processes. This study presents the synthesis of facet-controlled molybdenum phosphide (MoP) single crystals using a liquid-metal-assisted chemical vapor deposition method. By adjusting the synthesis temperature, two distinct MoP morphologies are created: nanoplates dominated by (0001) facets and pillars dominated by $\left(10\overline{1}0\right)$ facets. Electrochemical evaluation reveals that the MoP pillars outperform nanoplates in the two-electron oxygen reduction reaction, achieving over 92% selectivity for H₂O₂ production and significantly higher kinetic current density. Long-term stability tests confirm that the MoP pillars maintain a high Faradaic efficiency (>90%) and stable electrosynthesis over 80 h of continuous operation, highlighting their robustness. Density functional theory calculations reveal that the $\left(10\overline{1}0\right)$ facets of the pillars enhance catalytic activity by reducing the OOH adsorption strength, thereby lowering the overpotential. This study underscores the importance of facet engineering in optimizing catalytic performance and provides a pathway for designing advanced TMP-based materials for energy and environmental applications.