In time dependent (classical or quantum) particle-based simulators, one needs an algorithm to determine when (and with which properties) electrons are injected from the reservoir into the simulation box. In this work we develop an electron injection model for 2D materials with linear-dispersion materials. The injected model is based on satisfing the required phase-space density of electrons. In particular, we discuss the differences between a garphene-based electron injection model and older models developed for parabolic-dispersion materials. The linear dispersion of graphene implies unexpected restrictions when developing the injection model. © 2014 IEEE.