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Rhodium Nanoparticle Shape Dependence in the Reduction of NO by CO

“…Evidence from measured activation energies, however, implies more complexity, as shown in Table 1. Although the activation energies for CO 2 and N 2 O formation on the nanopolyhedra catalysts are similar to those previously reported for this reaction on Rh (111) single crystals [17], the measured activation energies for CO 2 and N 2 O formation on the nanocube catalysts are intermediate to the two separate temperature regimes reported previously on Rh (100) single crystals [13]. Rh (100) single crystals have been reported to feature both a low temperature regime with higher activation energies for all products and a high temperature regime with lower activation energies for all products starting at about 315°C [13,15].…”

“…Previous reports in this temperature range have found higher TOFs for Rh (100) single crystals than for Rh (111) single crystals [13,17]. Both Rh (100) and Rh (111) single crystals are strongly selective towards N 2 O in this temperature range [13,17]. The similarities in the trends between these single crystal results and the shape-dependent results presented here for (111)-dominated nanopolyhedra and (100)-dominated nanocubes indicate that the effect of surface structure on TOF and selectivity is similar in both nanoparticle and single crystal regimes.…”

“…Previous reports in this temperature range have found higher TOFs for Rh (100) single crystals than for Rh (111) single crystals [13,17]. Both Rh (100) and Rh (111) single crystals are strongly selective towards N 2 O in this temperature range [13,17].…”

“…The reaction proceeds much faster on Rh than on Pd or Pt [12] and is known to be structure sensitive on Rh single crystals [13]. The products of the reaction are CO 2 at all temperatures, N 2 O primarily (*75%) at the lower (\320°C) temperatures investigated in this study, and N 2 primarily at higher temperatures ([320°C) [12].…”

“…3. The activation energies as calculated from the accumulation of each product from 230 to 270°C are presented in Table 1 for both the nanopolyhedra and nanocube catalysts, as compared to single crystal data taken at similar temperatures and pressures [13,17]. The measured TOFs were higher for the nanocube catalysts than for the nanopolyhedra catalysts at all temperatures.…”