Ultralow overpotential nitrate reduction to ammonia via a three step relay mechanism

AbstractAmmonia plays a significant role in agriculture and the next-generation carbon-free energy supply. Electrocatalytic nitrate reduction to NH3is attractive for nitrate removal and NH3production under ambient conditions. However, the energy efficiency is limited by the high reaction overpotential. Here, we propose a three-step relay mechanism composed of a spontaneous redox reaction, electrochemical reduction, and electrocatalytic reduction to overcome this issue. RuxCoyalloys are designed and adopted as model catalysts. Ru15Co85exhibits an onset potential of +0.4 V versus a reversible hydrogen electrode and an energy efficiency of 41.54 ± 1.72 %, which are both the best records. The high performance results in a low production cost of $0.49 ± 0.02 /kgammonia($0.58~1.02/kgammoniasold in the USA). Electrochemicalin situspectroscopy and theoretical simulations indicate that the three-step relay mechanism leads to excellent catalytic performance on Ru15Co85and can be extended to RuxFeyand RuxNiyalloys.