Tandem Electrocatalytic Reduction of Nitrite to Ammonia on Rhodium–Copper Single Atom Alloys

Abstract

Electrocatalytic reduction of NO2− to NH3 (NO2RR) presents a fascinating approach for simultaneously migrating NO2− pollutants and producing valuable NH3. In this study, single‐atom Rh‐alloyed copper (CuRh1) is explored as a highly active and selective catalyst toward the NO2RR. Combined theoretical calculations and in situ FTIR/EPR spectroscopic experiments uncover the synergistic effect of Rh1 and Cu to promote the NO2RR energetics of CuRh1 through a tandem catalysis pathway, in which Rh1 activates the preliminary adsorption and hydrogenation of NO2− (NO2− → *NO2 → *NOOH → *NO), while the generated *NO on Rh1 is then transferred on Cu substrate which promotes the rate‐determining step of *NO → *NHO toward the NH3 synthesis. As a result, CuRh1 equipped in a flow cell presents an unprecedented NH3 yield rate of 2191.6 µmol h−1 cm−2 and NH3‐Faradaic efficiency of 98.9% at a high current density of 322.5 mA cm−2, as well as long‐term stability for 100 h electrolysis.

Magneto-electrochemical ammonia synthesis: Boosting nitrite reduction activity by the optimized magnetic field induced in spin polarized system

“…MnPc in the presence of a magnetic field (with 0.2 M SO4and in a NO2-free electrolyte), shows a stronger TEMPO-H signal than MnPc without any magnetic field (SI), suggesting that MnPc (with 95 mT) is more effective than MnPc (with 0 mT) in dissociating H2O and generating H radicals. [55][56][57] Nevertheless, the TEMPO-H signal intensity of MnPc (with 0 mT) decreased when 0.1 M NO2 − was added to the system, whereas the TEMPO-H signal of MnPc (with 95 mT) highest decreased (SI), suggesting MnPc (with 95 mT) increases the hydrogenation in NO2by consumes H radicals to form ammonia.…”

Electrosynthesis of Ammonia from Nitrate Using a Self-Activated Carbon Fiber Paper

“…NO 3 RR involves complex reaction pathways that require multiple electron and proton transfer (NO 3 – + 6H 2 O + 8e – → NH 3 + 9OH – ), and the electrocatalysts that can efficiently drive this reaction are mainly based on metals, particularly noble metals such as ruthenium, palladium, and rhodium so far. − Their scarcity and high cost drive efforts to develop nonmetallic catalysts for industrial-scale NH 3 production. Although nonmetallic catalysts including defective graphene, carbon nitride, heteroatom-doped carbon, boron carbide, and so on have been demonstrated to deliver decent catalytic performance for various crucial reactions (e.g., HER, ORR, CO 2 RR, and NRR), − there are surprisingly few reports for NO 3 RR and typically their NH 3 yield rates are much lower than that of state-of-the-art metal-based catalysts. − To date, it is still challenging to overcome the bottleneck of slow reaction kinetics and severe side reactions on nonmetallic electrocatalysts.…”

Efficient Synthesis of Co-Based Electrocatalysts from Waste Batteries and Distillers’ Grains toward Nitrate Wastewater to Ammonia

“…In contrast to conventional methods, electrochemical nitrate reduction is an important alternative technology that can reduce harmful nitrate to a high value-added product ammonia, which can be further converted into organic fertilizers . In recent years, with the development of electrocatalysis technology, − the electrocatalytic mechanism for nitrate reduction to ammonia synthesis has been gradually revealed, and new types of electrode materials have been emerging. − Among them, transition-metal Co-based materials are widely used as effective electrocatalysts for nitrate reduction to ammonia synthesis. However, their source is often from expensive Co chemical compounds, which not only cause a waste of resources but also may produce secondary pollution caused by Co overflow .…”