The potential applications of composite nanostructured materials for PETE (photon-enhanced thermionic emission for solar concentrators) and thermionic plasma energy systems electrode implementation are considered in this study. The investigation of composite porous silicon (PS) and graphene-based structures for PETE and thermionic energy converter (TEC) electrode realization is presented. The origins of low work function effect are considered and interpreted as a repercussion of surface modification and structure alteration on the composite material properties. The significant decrease in the effective electron work function to an anomalously low value of 1 eV is obtained with a perforated nickel anode functionalized with nanosized graphene layers. SEM X-ray microanalysis of the TEC collector surface is performed, the mechanism of the anode work function lowering effect is considered. Raman spectroscopy technique is utilized in order to investigate the surface structure properties of PS-based composite layers (PS/Ag). The interpretation of PS/Ag Raman spectra is proposed.