Researchers examined oxygen adsorption on gold surfaces, measuring both sticking probability and the energy needed to dissociate the molecule. They found the hexagonal bulk facet barely captures O₂, leaving the bond untouched and demanding high dissociation energy. By contrast, the square lattice readily adsorbs O₂, deforms it and splits it, giving gold catalytic activity comparable to platinum.

Gold atoms migrate to form a repeating pattern that covers the face; the unit cell spans a large area, so bulk pieces have enough atoms to complete the transition and become inert. Nanoparticles, however, contain too few atoms to undergo this reconstruction, leaving square facets that behave like catalysts. Consequently, the surface energy landscape shifts, making the square facet thermodynamically favored on tiny particles.

The study shows that merely shrinking gold from macroscopic chunks to nanoscale particles flips its surface chemistry, turning a historically inert metal into a reactive platform. This insight gives materials scientists a lever to tune catalytic performance by engineering facet geometry rather than alloying. Even if gold remains expensive, its controllable activity could inspire niche applications where durability outweighs cost.