Iridium-incorporated cobalt hydroxide electrodeposited on titanium meshes enabling electroreduction of nitrate and nitrobenzene to ammonia and aniline

Abstract

The electrocatalytic nitrate reduction reaction (NO₃RR) represents a feasible approach for the removal of harmful contaminants and the synthesis of green ammonia (NH₃). However, a significant challenge associated with NO₃RR is its sluggish kinetics. In this study, we constructed an iridium-incorporated cobalt hydroxide electrode deposited on titanium meshes (Ir@Co(OH)₂/TM), which exhibits an impressive Faraday efficiency (FE) of 91.6 ± 2.2% at −0.2 V versus the reversible hydrogen electrode, as well as the highest NH₃ yield of 927.3 ± 19.6 μmol h⁻¹ cm⁻² at −0.5 V. Furthermore, Ir@Co(OH)₂/TM maintains exceptional activity in simulated wastewater, achieving a notable NH₃ yield of 901.0 ± 71.6 μmol h⁻¹ cm⁻² with an FE of 92.7 ± 6.3% at −0.5 V. The electrode also demonstrates satisfactory performance in both alkaline media with varying NO₃⁻/OH⁻ concentrations and neutral media, indicating its broad applicability. Additionally, the minor fluctuations in current densities, NH₃ yields, and FEs observed during the 12 hours stability test and the 20-cycle test confirm the outstanding stability and durability of Ir@Co(OH)₂/TM. Notably, Ir@Co(OH)₂/TM can also facilitate the electroreduction of nitrobenzene (Ph-NO₂) to aniline (Ph-NH₂), achieving a remarkable Ph-NO₂ conversion of 90.6% and a Ph-NH₂ selectivity of 71.6% at −0.5 V. This study presents a viable method for the efficient fabrication of bifunctional electrocatalysts aimed at enhancing the production of high-value chemicals from environmental contaminants.