An interfacial synergism effect of Pd-g-C3N4 in Pd/g-C3N4 for highly active and selective hydrogenation of 4-nitrophenol.

Abstract

Herein, we report that Pd nanoparticles (NPs) anchored on graphitic nitride carbon (Pd/g-C3N4) catalysts with various Pd contents (1.55 wt%, 0.14 wt%, 0.04 wt%) are successfully prepared via a simple NaBH4 reduction method, exhibiting excellent catalytic activity and selectivity toward 4-aminophenol (4-AP) in 4-nitrophenol (4-NP) selective hydrogenation. 4-NP is completely converted to 4-AP (yield ∼ 100%) under quite moderate reaction conditions (40 °C, 2.0 MPa H2 and 5 min) over the 1.55 wt% Pd/g-C3N4 catalyst, with a high reaction rate r = 134.4 mol4-NP molPd-1 min-1. The excellent catalytic performance can be attributed to the following reasons: (1) a higher ratio of Pd(0)/Pdn+ provides much more exposed active sites for the potential adsorption and activation of the reactants, which is beneficial for increasing the reaction rate and catalytic activity; (2) Pd NPs are highly dispersed on g-C3N4 due to the strong interaction of Pd-N or Pd-C; (3) the interfacial synergism effect between Pd NPs and g-C3N4 enables the effective adsorption and activation of H2 (4-NP) at Pd (g-C3N4), promoting the catalytic hydrogenation of 4-NP and improving their catalytic properties. In addition, this catalyst has superior reusability.