Interfacial engineering of Cu-Fe2O3 nanotube arrays with built-in electric field and oxygen vacancies for boosting the electrocatalytic reduction of nitrates

The key to enhancing electrocatalytic nitrate reduction to ammonium (ENRA) is to improve the slow mass transfer of nitrates and the effective electron transfer on the catalyst surface. Based on the thermal diffusion theory and electroreduction mechanism, a Cu-Fe2O3 nanotube electrocatalyst with enriched oxygen vacancies and a built-in electric field was designed by controlling the heating and electroreduction time. Because of its unique structure, it could induce the generation of a built-in electric field and promote the enrichment of nitrate ions and electron transfer on the catalyst surface. Combined with the oxygen vacancy (OV)-anchoring mechanism, Cu-Fe2O3-60 showed remarkable Faraday efficiency (80.1%) and selectivity (88.47%). In addition, even when the reactor was scaled up to a pilot capacity of 180 L, the conversion rate was close to 85%. This work demonstrates that controlling the staggered interface distribution and oxygen vacancy number in metal-semiconductor is an effective way to design high-efficiency electrocatalysts.