The low temperature adsorption of N2 on Rh/SiO2 samples of various particle-size distributions was followed by FTIR. The addition of O2 pulses on Rh0 surfaces saturated with chemisorbed N2 allowed us to reassign stretching frequencies attributed originally to N2-Rh0 to N2-RhΔ+. The formation of the latter oxidized Rh species is assumed to be induced by electron withdrawing from adsorbed oxygen species on Rh surface centers neighboring to those onto which N2 species are chemisorbed. The present work, thus, enables us to delimit ranges of frequencies for which the adsorption of N2 can be considered to occur on either Rh0 or RhΔ+ centers for ΝN2 lower or higher than 2243 cm-1, respectively. The N2-FTIR experiments performed on the studied catalysts also suggest a lattice plane-selectivity for N2 adsorption on metallic Rh planes of different natures which, to our knowledge, has not been reported yet for Rh.