Conjugated Coordination Polymer as a New Platform for Efficient and Selective Electroreduction of Nitrate into Ammonia

Abstract

Electroreduction of nitrate into ammonia (NRA) provides a sustainable route to convert the widespread nitrate pollutants into high‐value‐added products under ambient conditions, which unfortunately suffers from unsatisfactory selectivity due to the competitive hydrogen evolution reaction (HER). Previous strategies of modifying the metal sites of catalysts often met a dilemma for simultaneously promoting activity and selectivity toward NRA. Here, a general strategy is reported to enable an efficient and selective NRA process through coordination modulation of single‐atom catalysts to tailor the local proton concentration at the catalyst surface. By contrast, two analogous Ni‐single‐atom enriched conjugated coordination polymers (NiO4‐CCP and NiN4‐CCP) with different coordination motifs are investigated for the proof‐of‐concept study. The NiO4‐CCP catalyst exhibits an ammonia yield rate as high as 1.83 mmol h−1 mg−1 with a Faradaic efficiency of 94.7% under a current density of 125 mA cm−2, outperforming the NiN4‐CCP catalyst. These experimental and theoretical studies both suggest that the strategy of coordination modulation can not only accelerate the NRA by adjusting the adsorption energies of NRA intermediates on the metal sites but also inhibit the HER through regulating the proton migration with contributions from the metal‐hydrated cations adsorbed at the catalyst surface, thus achieving simultaneous enhancement of NRA selectivity and activity.

Laser-controlled tandem catalytic sites of CuNi alloys with ampere-level electrocatalytic nitrate-to-ammonia reduction activities for Zn–nitrate batteries

“…3h and Tables S2, S3 (ESI †). 3,8,9,12,30,31,[33][34][35][36] To further confirm the NIRR activity origin of the CuNi NPs/ CF, we analyzed the NO 3 À reduction process by the electrochemical active surface areas (ECSA) in 1 M NaOH with 44.3 g L À1 NO 3 À . The ECSA was evaluated by the electrochemical double-layer capacitances in the non-faradaic interval, which played a prominent role in calculating the kinetic parameters of the electrochemical reaction.…”

Tungsten Nitride/Tungsten Oxide Nanosheets for Enhanced Oxynitride Intermediate Adsorption and Hydrogenation in Nitrate Electroreduction to Ammonia

“…This result reveals that *NO 3 and *NO 2 can be strongly adsorbed and exhibit enhanced NO 3 RR processes on WN/WO 3 and WN surfaces compared to WO 3 . The downward peaks at 1460 cm –1 can be ascribed to stretching vibration of N–H in *NH 3 intermediates, meaning the desorption of *NH 3 to form NH 3 . The downward absorption band in the vicinity of 1650 cm –1 is due to the H–O–H bending vibration of H 2 O, reflecting the dissociation of H 2 O on the catalyst surface .…”

“…The downward peaks at 1460 cm −1 can be ascribed to stretching vibration of N−H in *NH 3 intermediates, meaning the desorption of *NH 3 to form NH 3 . 46 The downward absorption band in the vicinity of 1650 cm −1 is due to the H−O−H bending vibration of H 2 O, reflecting the dissociation of H 2 O on the catalyst surface. 47 Compared with 6e, the peak areas of *NO 3 show that the consumption of *NO 3 on WO 3 is much lower than that of WN/WO 3 and WN.…”

Anchoring Ru nanoclusters to defect-rich polymeric carbon nitride as a bifunctional electrocatalyst for highly efficient overall water splitting

“…21,22 However, current synthetic strategies for conning Ru NCs in nitrogen-doped carbon matrices include annealing at high temperature (>700 °C) under the erosive NH 3 atmosphere, pulsed laser deposition, and the coupling of multi-step procedures, which obviously suffer from limitations of tedious process, insufficient controllability, and poor universality. [23][24][25] Graphitic carbon nitride (g-C 3 N 4 ), a nitrogen-rich carbon matrix, has attracted more attention due to its high abundance, low cost and accessible preparation features. 26,27 Furthermore, nitrogen vacancies (V N ) can be easily introduced into g-C 3 N 4 during its synthesis, which can efficiently modulate the electronic structure and charge transfer.…”