Electronic State and Microenvironment Modulation of Metal Nanoparticles Stabilized by MOFs for Boosting Electrocatalytic Nitrogen Reduction

Modulation of the local electronic structure and microenvironment of catalytic metal sites plays a critical role in electrocatalysis, yet remains a grand challenge. Herein, PdCu nanoparticles with an electron rich state are encapsulated into a sulfonate functionalized metal-organic framework, UiO-66-SO3H (simply as UiO-S), and their microenvironment is further modulated by coating a hydrophobic polydimethylsiloxane (PDMS) layer, affording PdCu@UiO-S@PDMS. This resultant catalyst presents high activity toward the electrochemical nitrogen reduction reaction (NRR, Faraday efficiency: 13.16%, yield: 20.24 mu g h(-1) mg(cat.)(-1)), far superior to the corresponding counterparts. Experimental and theoretical results jointly demonstrate that the protonated and hydrophobic microenvironment supplies protons for the NRR yet suppresses the competitive hydrogen evolution reaction reaction, and electron-rich PdCu sites in PdCu@UiO-S@PDMS are favorable to formation of the N2H* intermediate and reduce the energy barrier of NRR, thereby accounting for its good performance.

Automated summary

In this study, PdCu nanoparticles were encapsulated into a sulfonate functionalized metal-organic framework, UiO-66-SO3H, and their microenvironment was further modified by coating a hydrophobic polydimethylsiloxane (PDMS) layer. The resulting PdCu@UiO-S@PDMS catalyst exhibited high activity towards electrochemical nitrogen reduction reaction (NRR), surpassing other counterparts. Experimental and theoretical results revealed that the protonated and hydrophobic microenvironment provided protons for NRR and suppressed the competitive hydrogen evolution reaction, while the electron-rich PdCu sites favored the formation of the N2H* intermediate and reduced the energy barrier of NRR, contributing to its excellent performance.