Cascade Electrocatalytic Nitrate Reduction Reaching 100% Nitrate-N to Ammonia-N Conversion over Cu 2 O@CoO Yolk-Shell Nanocubes.

The electroreduction of nitrate to ammonia via a selective eight-electron transfer nitrate reduction reaction offers a promising, low energy consumption, pollution-free, green NH 3 synthesis strategy alternative to the Haber-Bosch method. However, it remains a great challenge to achieve high NH 4 + selectivity and complete conversion from NO 3 - -N to NH 4 + -N. Herein, we report ingredients adjustable Cu 2 O@CoO yolk-shell nanocubes featured with tunable inner void spaces and diverse activity centers, favoring the rapid cascade conversion of NO 3 - into NO 2 - on Cu 2 O and NO 2 - into NH 4 + on CoO. Cu 2 O@CoO yolk-shell nanocubes exhibit super NH 4 + Faradaic efficiencies (>99%) over a wide potential window (-0.2 V to -0.9 V versus RHE) with a considerable NH 4 + yield rate of 15.27 mg h -1 cm -2 and fantastic cycling stability and long-term chronoamperometric durability. Cu 2 O@CoO yolk-shell nanocubes exhibited glorious NO 3 - -N to NH 4 + -N conversion efficiency in both dilute (500 ppm) and highly concentrated (0.1 and 1 M) NO 3 - electrolytes, respectively. The nitrate electrolysis membrane electrode assembly system equipped with Cu 2 O@CoO yolk-shell nanocubes delivers over 99.8% NH 4 + Faradaic efficiency at cell voltages of 1.9-2.3 V.