Uniform octahedral ZrO2@C from carbonized UiO-66 for electrocatalytic nitrogen reduction

The electrochemical ammonia synthesis under ambient conditions is a promising process instead of the energy-intensity Haber-Bosch process with the release of huge greenhouse gases. But it still faces sluggish catalytic kinetics owing to difficulty of N2 adsorption and N≡N bond cleavage. Herein, the uniform ZrO2@C with octahedral structure is synthesized via two-step annealing treatment of UiO-66. The formation of ZrO2 originates from Zr and O elements in UiO-66, and the grain size is confined by the produced carbon matrix from the carbonization of the organic ligand, resulting in more exposure of the active sites. ZrO2@C obtained at 650 °C presents excellent electrocatalytic nitrogen reduction performance with a NH3 yield rate of 6.72 μg h−1 mgcat.−1 and a Faradaic efficiency of 2.68% at −0.6 V versus reversible hydrogen electrode (RHE). This work provides a strategy to design metal [email protected] from metal-organic frameworks for nitrogen fixation.