Piezo-enhanced activation of dinitrogen for room temperature production of ammonia

Abstract

The catalytic conversion of nitrogen to ammonia remains an energy-intensive process, demanding advanced concepts for nitrogen fixation. The major obstacle of nitrogen fixation lies in the intrinsically high bond energy (941 kJ mol^-1) of the N≡N molecule and the absence of a permanent dipole in N₂. This kinetic barrier is addressed in this study by an efficient piezo-enhanced gold catalysis as demonstrated by the room temperature reduction of dinitrogen into ammonia. Au nanostructures were immobilized on thin film piezoelectric support of potassium sodium niobate (K_0.5Na_0.5NbO₃, KNN) by chemical vapor deposition of a new Au(III) precursor [Me₂Au(PyTFP)(H₂O)]1(PyTFP = (Z)-3,3,3-trifluoro-1-(pyridin-2-yl)-prop-1-en-2-olate) that exhibited high volatility (60 °C, 10^-3mbar) and clean decomposition mechanism to produce well adherent elemental gold films on KNN and Ti substrates. The gold-functionalized KNN films served as an efficient catalytic system for ammonia production with a Faradaic efficiency of 18.9% achieved upon ultrasonic actuation. Our results show that the spontaneous polarization of piezoelectric materials under external electrical fields augments the sluggish electron transfer kinetics by creating instant dipoles in adsorbed N₂molecules to deliver a piezo-enhanced catalytic system promising for sustained activation of dinitrogen molecules.

Keywords: CVD; gold nanostructures; gold precursor; nitrogen reduction reaction.