Screening of transition metal oxides for electrocatalytic nitrate reduction to ammonia at large currents

Electrochemical nitrate reduction reaction (NO₃RR) towards ammonia, as an emerging and appealing technology alternative to the energy-intensive Haber–Bosch process and inefficient nitrogen reduction reaction, has recently aroused wide concern and research. However, the current research of the NO₃RR towards ammonia lacks the overall performance comparison of various electrocatalysts. Given this, we here make a comparison of 12 common transition metal oxide catalysts for the NO₃RR under a high cathodic current density of 0.25 A·cm⁻², wherein Co₃O₄ catalyst displays the highest ammonia Faradaic efficiency (85.15%) and moderate activity (ca. −0.25 V vs. reversible hydrogen electrode). Other external factors, such as nitrate concentrations in the electrolyte and applied potential ranges, have also been specifically investigated for the NO₃RR.