New electron transfer bridge construction between Ni3(HTTP)2 and graphene oxide layers for enhanced electrocatalytic oxidation of tetracycline hydrochloride

• 1. Ni and S atoms in Ni 3 (HTTP) 2 /GO had negligible contributions for catalysis directly. • 2. Electron transfer via “GO-C-O-S-C-Ni 3 (HTTP) 2 ” bridge was important for catalysis. • 3. S atoms were more favorable for generating connection bridges than N and O atoms. Electron transfer capability as crucial properties of anode is directly related to electrocatalytic performance. However, the contributions of electron transfer were always under estimated due to the ambiguous mechanism of electrocatalysis. In this paper, a new electron transfer bridge was constructed in Ni 3 (HTTP) 2 /GO to provide a new insight into electrocatalytic performance enhancement. The contributions of active sites candidates, including metal sites, ligands (metal bridging atoms), and electron transfer bridges were innovatively separated. As replacement experimental results (of metal sites and metal bridging atoms), both metal sites and metal bridging atoms contributed slightly as the active center directly for the electrocatalytic degradation of tetracycline hydrochloride (TCH). The great improvement was attributed to the generation of “GO-C-O-S-C-Ni 3 (HTTP) 2 ” bridges, in which S atoms from ligands were critical anchoring sites for the connection of two 2D layers (Ni 3 (HTTP) 2 and GO layer). The experimental and density functional theory results showed Ni 3 (HTTP) 2 could donate electrons to GO layers, leading the electrostatic imbalance of charge density to facilitate electron withdrawal from pollutions (not only TCH, but also dyes and complex microbial flora). The results of this paper provide a new strategy for improving electrocatalytic efficiency by adjusting electron transfer for novel practical applications of Ni 3 (HTTP) 2 /GO composites.