The review of recent theoretical and experimental research on the complex surface chemistry processes that evolve from low-Z material conditioning on plasma-facing materials under extreme fusion plasma conditions is presented. A combination of multi-scale computational physics and chemistry modeling with real-time diagnosis of the plasma-material interface in tokamak fusion plasma edge is complemented by ex-vessel in-situ single-effect experimental facilities to unravel the evolving characteristics of low-Z components under irradiation. Effects of the lithium and boron coatings at carbon surfaces to the retention of deuterium and chemical sputtering of the plasma-facing surfaces are discussed in detail. The critical role of oxygen in the surface chemistry during hydrogen-fuel irradiation is found to drive the kinetics and dynamics of these surfaces as they interact with fusion edge plasma that ultimately could have profound effects on fusion plasma confinement behavior. Computational studies also extend in spatio-temporal scales not accessible by empirical means and therefore open the opportunity for a strategic approach at irradiation surface science studies that combined these powerful computational tools with in-vessel and ex-vessel in-situ diagnostics.