Researchers reported a sulfur-anchoring method of high-temperature for the universal synthesis of small-sized intermetallic compounds (IMCs) fuel cell catalysts, successfully synthesized small-sized Pt intermetallic nanoparticle catalysts with ultralow Pt loading and high mass activity. They also synthesized intermetallic libraries of small nanoparticles consisting of 46combinations of platinum with 16 other metal elements and used them to study the dependence of electrocatalytic oxygen-reduction reaction activityon alloy composition and platinum skin strain.
Fig.1 Schematic illustration of the high-temperature sulfur-anchoring synthetic IMCs catalyst.
Intermetallic compounds (IMCs, also known as atomically ordered alloys) attracted wide attention because of their unique atomically ordered properties and excellent catalytic performance in many chemical reactions.In particular, Pt-based IMCs are expected to provide a new generation of low Pt cathode oxygen reduction catalysts PEM fuel cells and significantly reduce the cost of membrane electrode assembly.Although the IMC structure is thermodynamically a stable phase compared to the conventional disordered solid solution alloy structure, the synthesis of IMCs often requires high-temperature heat treatment to overcome the kinetic energy barriers to ordered rearrangement of atoms in the solid phase (Fig. 2A). However, inevitable metal sintering at high temperature is undesired during the synthesis of IMCs, as it will lead to larger crystallites.(Fig.2B) Thus, it results in a decreased specific surface area and lower catalytic activities of the materials, and eventually reduce the utilization rate of Pt, therefore greatly increasing the cost of fuel cells. Therefore, developing methods for the synthesis of small-size Pt-based IMCs catalysts is critical to significantly lowering the cost of fuel cells.
Fig2. (A)Schematic illustration showing the kinetic energy barrier for atom ordering in the disorder-to-order transition; (B)Schematic illustration showing the dilemma of simultaneously accelerated sintering kinetics and atom ordering kinetics with temperature;(C)Schematic illustration of the high-temperature sulfur-anchoring synthetic approach.