Unlocking the Power of PtMo Catalysts: A Deep Dive into Electrocatalytic Activity

The role of molybdenum (Mo) in platinum-molybdenum (PtMo) catalysts has gained significant attention in recent years, particularly in the context of enhancing electrocatalytic activity for reactions such as CO oxidation. Researchers have attributed the improved performance of PtMo catalysts to the presence of oxygenated species on the surface of catalyst particles. These Mo oxy-hydroxide species, as revealed through X-ray absorption near-edge structure (XANES) studies, play a crucial role in facilitating oxygen transfer, which is essential for catalytic reactions.

The electronic properties of the PtMo catalyst vary with applied potential, as highlighted by Mukerjee and colleagues. Their findings indicate that the oxidation state of Mo changes, shifting from +V at 0.0 V to higher values as the potential increases. This shift suggests that the interaction between Pt and Mo alters under different electrochemical conditions, affecting the catalysts' overall activity. The d band vacancy per Pt atom also increases at higher potentials, which is a significant factor in enhancing catalytic performance.

However, when comparing PtMo with other alloy catalysts like platinum-ruthenium (PtRu), notable differences arise. While PtMo catalysts exhibit promising characteristics, they do not perform as effectively for the oxidation of methanol and ethanol as PtRu catalysts do. This discrepancy can be attributed to the structural differences between the materials and the specific atomic arrangements that affect reaction pathways. The necessity of ensembles of active atoms for dehydrogenation reactions further complicates the performance of PtMo, as these ensembles are disrupted by the presence of Mo.

One of the challenges in optimizing PtMo alloys is achieving a well-mixed structure. Studies have shown that the fraction of Mo in the first coordination shell of Pt atoms is often lower than expected, suggesting that the Mo does not integrate seamlessly into the Pt matrix. To address this, researchers have developed methods to ensure that Mo is closely associated with Pt, utilizing controlled surface reactions that modify the Pt surface with small amounts of Mo. This approach has demonstrated improved CO tolerance at low potentials, corroborating the beneficial role of Mo oxy-hydroxides.

Advancements in alloy catalyst research, such as the investigation of PtSn/C catalysts, further emphasize the potential of modifying traditional platinum catalysts. These studies reveal that different alloy compositions can lead to enhanced catalytic activity for specific reactions, including methanol oxidation. By understanding the underlying mechanisms and optimizing the structural composition of these catalysts, researchers are paving the way for more efficient and effective electrocatalytic materials in energy conversion applications.