My naïve take is liquid phase is higher energy than solid phase. The gallium here actually keeps the little amount of platinum liquid by diluting those platinum

My naïve take is liquid phase is higher energy than solid phase. The gallium here actually keeps the little amount of platinum liquid by diluting those platinum atoms into gallium-surrounding the platinum so it can’t solidify. Thus the catalytic effects are more like a liquid platinum catalyst than solid. Neat trick that probably wasn’t obvious outside of new methods. Edit-also note, this may be more like alchemy. They’re seeing the atoms on the surface performing the catalytic effect but the platinum resides below the surface. So the nearby platinum atoms are making the gallium mimic platinum properties.