Rational design of an Fe cluster catalyst for robust nitrogen activation

Ammonia synthesis by the electrochemical technique is a promising solution to replace the energy-intensive Haber–Bosch process in industry, which inevitably requires high-performance catalysts. However, the development of catalysts is still limited by the inferior activation of the stable NN bond. Herein, a robust N2-activation mode is proposed, which addresses the electron donation mechanism to both the N2 antibonding orbitals of py and pz, simultaneously. Following this strategy, the single cluster catalyst (SCC) of Fe4/GaS has realized remarkable nitrogen reduction reaction (NRR) performance with an ultra-low overpotential (η) of 0.08 V by density functional theory (DFT) calculations. N2 is completely activated in a side-on adsorption configuration on the hollow site of Fe4/GaS, where both degenerate N2–π* orbitals are properly hybridized to the frontier orbitals of the Fe4 cluster, as proven by fragment orbital analysis. This work proposes an efficient strategy for N2 activation, and also provides a valid design guideline for further research.