Synergistic Band Gap Narrowing and Interfacial Electron Flow in Pd-Embedded NiCo-LDH for High-Efficiency Glycerol Electrooxidation

Synergistic processes of oxidation and adsorption of glycerol as a nucleophilic reagent during electrooxidation are of great importance, underscoring the need for a more comprehensive understanding of the adsorption and oxidation processes during glycerol electrooxidation. Herein, a unique structure of PdNP/NiCo, in which the Pd nanoparticles (NPs) (2.38 nm) were embedded in NiCo-layered double hydroxides (NiCo-LDH, denoted as NiCo), was constructed to synergistically enhance the oxidation and adsorption of glycerol molecules through narrowing the band gap and promoting the electronic metal–support interaction (EMSI)-induced interfacial electron-directed flow of the catalyst. The PdNP/NiCo achieved outstanding glycerol oxidation reaction (GOR) performance, requiring only 1.30 and 1.36 V (vs RHE) to achieve current densities of 10 mA cm–2 and 100 mA cm–2, respectively. Furthermore, comprehensive experimental and spectroscopic characterization confirmed that the successful embedding of Pd NPs into the NiCo-LDH effectively induced band gap narrowing of NiCo from 2.85 to 2.30 eV and promoted the formation of the oxidatively active Ni3+–O species, thereby enhancing the electrooxidation process. Concurrently, the incorporated Pd nanoparticles significantly improved the glycerol adsorption capacity. The density functional theory (DFT) calculations revealed a significantly lower deprotonation energy barrier of 0.15 eV and easier generation of the active species Ni3+–O for PdNP/NiCo compared to NiCo. In addition, the glycerol molecules located at the Pd–NiCo interface showed the most negative adsorption energy barrier compared with those of NiCo and Pd NPs, which was due to the strong electronic metal–support interaction (EMSI) at the interface between Pd NPs and NiCo-LDH.