Hollow N-doped carbon nanocages anchoring Ni-Ru bimetallic nanoparticles for enhanced peroxidase-like activity

Hollow structured composites with various elemental compositions and complex shell architectures exhibit great potential in application of heterogeneous catalysis. However, the synthesis of bimetallic alloy nanoparticles (NPs) supported by hollow carbon nanocages is a serious challenge. Herein, we report a streamlined synthesis of hollow spherical Ni/Ru bimetallic NPs embedded in N-doped hollow carbon nanocages (Ni/Ru@HNCs) via a carbonized organic polymer-mediated hard-templating strategy. Core-shell structured SiO₂@polydopamine-Ni²⁺ (PDA-Ni²⁺) composites are firstly prepared through a one-pot method. Subsequent high-temperature carbonization and KOH etching generate Ni@HNCs featuring a hollow architecture, high specific surface area, abundant active sites, and efficient mass transport. Ru species are then introduced hydrothermally, where a spontaneous galvanic replacement reaction between metallic Ni and Ru³⁺ ions drives the in situ formation and uniform anchoring of Ni-Ru alloy NPs on the N-doped carbon framework. The resultant Ni/Ru@HNCs exhibit exceptional peroxidase-mimicking activity, efficiently catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to yield a vivid blue product (oxTMB). Capitalizing on this robust catalytic performance, a sensitive colorimetric sensing platform is established for the rapid and selective detection of tea polyphenols (TP). This work not only demonstrates a rational design of high-performance bimetallic nanozymes with precisely controlled structure and composition but also provides a versatile, scalable strategy for developing advanced enzyme-mimetic materials for biosensing and food safety applications.