Electrochemically Selective Ammonia Extraction from Nitrate by Coupling Electron- and Phase-Transfer Reactions at a Three-Phase Interface

Abstract

As an attractive alternative to the Haber–Bosch process, an electrochemical process for nitrate (NO3 –) reduction to ammonia (NH3) has made great strides in the development of advanced electrocatalysts to suppress the unavoidable H2 evolution reaction (HER) and side production of N2. However, isochronous NH3 separation and recovery from the mother liquor, especially wastewaters, are awfully neglected in state-of-the-art electrochemical systems. Here, we designed electrochemical three-phase interfaces constructed by a CoP cathode and a flat-sheet gas membrane to achieve NO3 – reduction to ammonia and simultaneous NH3 recovery in the form of (NH4)2SO4 from wastewaters. The partial current density for ammonia yield and its recovery rate were 37.3 mA cm–2 and 306 g NH3-N m–2 day–1, respectively, accompanying 100% NO3 – removal and 99.7% NH3 extraction. By favoring the originally unfavored side reaction HER, it served as the driving force for NH3 separation from the wastewater through gas stripping and membrane separation at the three-phase interfaces. Unexpectedly, the timely NH3 separation could also promote the reduction of NO3 – to ammonia due to the release of much more active sites. From these, we envision that the present electrochemical process can be routinely employed as an effective strategy to address energy and environmental issues with NH3 recovery from NO3 – wastewater.

Lattice-strain and Lewis acid sites synergistically promoted nitrate electroreduction to ammonia over PdBP nanothorn arrays

“…Such a change in the electronic structure leads to PdBP NAs/NF having a higher surface adsorption capability of $H and therefore facilitates the hydrogenation reaction of intermediates in NO 3 À reduction but not the HER. 50 As for the P 2p spectrum (Fig. 3c), the peak at 130.58 eV corresponds to P(0), and the broad peak at around 133.4 eV is due to the formation of P-O species.…”

Engineering a Kesterite‐Based Photocathode for Photoelectrochemical Ammonia Synthesis from NOx Reduction

“…Furthermore, the PEC ammonia synthesis from wastewater is attempted. The simulated wastewater containing 0.05 m NO 3 − , 0.05 m SO 4 2– , and 0.07 m Cl − (a typical composition from nitrate rich industrial wastewater or waste brine) [ 59,60 ] has been used to evaluate the feasibility of using TiO x ‐250/CdS/CZTS photocathode for sustainably generating ammonia from wastewater. It is evidenced at −0.38V vs RHE, that 64.9% NH 4 + FE with yield rate of 6.54 µmol h −1 cm −2 can be achieved (Figure S29, Supporting Information).…”

Ultrasonic-Assisted Synthesis of CdS/Microcrystalline Cellulose Nanocomposites With Enhanced Visible-Light-Driven Photocatalytic Degradation of MB and the Corresponding Mechanism Study

“…The experimental procedure was the same as the photocatalytic activity test, but 50 ml of mixture of MB solution and scavenger, instead of 50 ml of MB solution was used. BQ (0.001 mol/L), TEOA (0.01 mol/L), and IPA (0.02 mol/L), were introduced into the reaction system as the scavengers for •O 2 − , h + , and •OH ( Zhu et al, 2016 ; Gao et al, 2021 ), respectively. As can be clearly seen from Figure 7 , the presence of TEOA, IPA and BQ all remarkably reduces the photocatalytic decolorization efficiency of MB under the same condition, which suggests that all •O 2 − , h + , and •OH participated in the decolorization reactions of MB.…”