Hydrogen incorporation at MoS \({}_2\) /SiO \({}_2\) interfaces governs charge doping, yet the atomistic transfer pathways and kinetic barriers depend strongly on the SiO \({}_2\) surface termination. Using first-principles simulations, we quantify hydrogen transfer barriers as a function of SiO \({}_2\) surface reconstruction and out-of-plane boundary conditions. We compare two reconstructed oxide terminations interfaced with monolayer MoS \({}_2\) . At interfaces with dangling bonds, H transfers barrier-free from MoS \({}_2\) to SiO \({}_2\) , while reverse transfer into defect-free MoS \({}_2\) remains kinetically blocked even in the presence of a sulfur vacancy (barrier >3 eV). At saturated interfaces, H transfers barrier-free from SiO \({}_2\) to MoS \({}_2\) , while subsurface-to-surface transfer has a barrier of \(\sim\) 0.4 eV. On MoS \({}_2\) , H transfers laterally with \(\sim\) 0.3 eV barriers, whereas incorporation into the monolayer requires \(\sim\) 0.7 eV. These results show that reconstruction-driven passivation reverses the preferred direction of interfacial H transfer and determines the preferred incorporation side.
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