An unsaturated metal site-promoted approach to construct strongly coupled noble metal/HNb3O8 nanosheets for efficient thermo/photo-catalytic reduction

Abstract

Creating two-dimensional (2D) crystal–metal heterostructures with an ultrathin thickness has spurred increasing research endeavors in catalysis because of its fascinating opportunities in tuning the electronic state at the surface and enhancing the chemical reactivity. Here we report a novel and facile Nb⁴⁺-assisted strategy for the in situ growth of highly dispersed Pd nanoparticles (NPs) on monolayer HNb₃O₈ nanosheets (HNb₃O₈ NS) constituting a 2D Pd/HNb₃O₈ NS heterostructure composite without using extra reducing agents and stabilizing agents. The Pd NP formation is directed via a redox reaction between an oxidative Pd salt precursor (H₂PdCl₄) and reductive unsaturated surface metal (Nb⁴⁺) sites induced by light irradiation on monolayer HNb₃O₈ NS. The periodic arrangement of metal Nb nodes on HNb₃O₈ NS leads to a homogeneous distribution of Pd NPs. Density functional theory (DFT) calculations reveal that the direct redox reaction between the Nb⁴⁺ and Pd²⁺ ions leads to a strong chemical interaction between the formed Pd metal NPs and the monolayer HNb₃O₈ support. Consequently, the as-obtained Pd/HNb₃O₈ composite serves as a highly efficient bifunctional catalyst in both heterogeneous thermocatalytic and photocatalytic selective reduction of aromatic nitro compounds in water under ambient conditions. The achieved high activity originates from the unique 2D nanosheet configuration and in situ Pd incorporation, which leads to a large active surface area, strong metal–support interaction and enhanced charge transport capability. Moreover, this facile Nb⁴⁺-assisted synthetic route has demonstrated to be general, which can be applied to load other metals such as Au and Pt on monolayer HNb₃O₈ NS. It is anticipated that this work can extend the facile preparation of noble metal/nanosheet 2D heterostructures, as well as promote the simultaneous capture of duple renewable thermal and photon energy sources to drive an energy efficient catalytic process.