Engineering CuO<sub><i>x</i></sub>Nanoparticles on Cu Foam for Acidic Nitrate Reduction to Ammonium
Maggie Lim, Jing Sun, Zhipeng Ma, Rouhollah Jalili, Rahman Daiyan, Emma C. Lovell, Rose Amal
Abstract
The electrochemical conversion of NO x (including NO 3 – and NO 2 – ) to ammonium using renewable energy is emerging as a green alternative pathway for decarbonization of high emission industry to meet net zero emission targets. The key to efficient NO x electrolysis relies on the understanding of surface chemistry to establish the structure–activity relationships that will govern future scaleup of this process. In this work, we have undertaken a mechanistic investigation, wherein by tuning the surface oxidation state of CuO x nanoparticles on Cu foam (referred as CuO x /CuF), we are able to investigate its impact on conversion of NO x to ammonium (NH 4 + ) under acidic reaction conditions. Supported by in situ Raman measurements, we reveal the importance of tuning the Cu oxidation state to maximize Cu 2 O formation, which forms beneficial Cu 2 O/Cu interfaces during reaction, allowing an enhanced NH 4 + yield with a production rate of 45 nmol s –1 cm –2 and Faradaic efficiency ( FE NH 4 + ) of 83% at −0.5 V vs RHE. Further, we reveal the promising stability of such interfaces under acidic conditions during long-term electrolysis for usage of up to 20 h.