The dependence of the work function of Pt(111) on surface carbon investigated with near ambient pressure X-ray photoelectron spectroscopy

Work function is one of the most useful and important parameters for metal surfaces in electronics and catalysis due to its sensitivity to surface chemistry and structure changes. Although work function is susceptible to various factors related to the surface, it does not provide further detailed information on the surface. Thus, it is crucial to have a way to investigate the surface structure and chemistry to understand the reasons for the work function change. Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) is a method used to simultaneously observe the surface chemistry and the corresponding change in work function. In this study, we report on the relationship between the surface abundance of carbon impurity and the work function of Pt(1 1 1). With AP-XPS experimental setup, we found that a small amount of surface carbon impurity is correlated with the significantly lowered work function of Pt(1 1 1) surface. This result suggests that a careful surface cleaning process is necessary, particularly for Pt-based single crystalline surfaces with high work functions to obtain true work functions. It is also necessary to control the gas environment and sample temperature to maintain the carbon-free surface and to monitor the surface chemical state.