Unveiling Structural Evolution of CO Adsorption on Ru(0001) with High-Resolution STM

CO adsorption on Ru(0001) provides fundamental information in related heterogeneous catalysis processes. High-resolution scanning tunneling microscopy achieved with a CO-modified tip uncovers the structural evolution of CO adsorption on Ru(0001) at different coverage. Precise molecular adsorption models are therefore given for (√3×√3)-R30°, (2√3×2√3)-R30°, and other relating structures developed at intermediate coverage. Direct experimental evidence confirms the tilted configuration of the CO molecules due to their lateral repulsion, which renews previous models for CO adsorption at high coverage. The microscopic observations therefore shed light on the formation mechanism of the CO superstructure formed on Ru(0001) at high coverage.