Adjustment of the single atom/nanoparticle ratio in Pd/CNT catalysts for phenylacetylene selective hydrogenation

Pd/C catalysts are widely used for hydrogenation reactions in the chemical industry. One of the reasons for their high activity is the ability of Pd nanoparticles (PdNP) to dissociate H2 and promote H-spillover. Nevertheless, for selective hydrogenation unpromoted Pd/C catalysts show disappointing results. The use of supported Pd single atom (PdSA) catalysts permits to achieve high selectivity. However, PdSA show low activity because they have difficulty in activating H2. A cooperative catalysis between PdNP and PdSA operates for the hydrogenation of alkenes thanks to the H-spillover, which makes it possible to obtain active isolated PdSA-H species. Here, we present experimental and computational results obtained for phenylacetylene hydrogenation on Pd/CNT catalysts showing different PdSA/PdNP ratios. Tuning this ratio allows doubling the activity while reaching high selectivity to styrene at high conversion. DFT calculations suggest that the first coordination sphere of PdSA has a pronounced effect on their reactivity.