Electroreduction of Nitrite to Ammonia Over Ni₁Ru Single‐Atom Alloys

Abstract

Electroreduction of nitrite to ammonia (NO2RR) holds great promise for concurrently achieving efficient NH3 electrosynthesis and wastewater purification. This study first develops Ni1Ru single‐atom alloys as an efficient and robust NO2RR catalyst. Extensive experiments and theoretical computations reveal that isolated Ni atoms electronically couple their adjacent Ru atoms to render Ni1Ru with high thermodynamic stability, boosted NO2−‐to‐NH3 hydrogenation energetics and suppressed hydrogen evolution. As a result, Ni1Ru assembled in a flow cell shows an exceptional NH3 yield rate of 37.5 mg h−1 cm−2 with an NH3‐Faradaic efficiency of 93.9% at a high current density of 312.3 mA cm−2, representing one of the highest NO2RR performances ever reported.

Electroreduction of Nitrite to Ammonia over a Cobalt Single-Atom Catalyst

“…As depicted in a high-angle annular dark-field scanned transmission electron microscopy (HAADF-STEM) image (Figure c), Co 1 /C 3 N 4 shows many bright spots (Co) that are atomically dispersed on the C 3 N 4 support. The isolated atomic dispersion of Co sites is further validated by the atomic line scanning plots (Figure d) and three-dimensional surface atom map (Figure e) . Elemental mapping images of Co 1 /C 3 N 4 reveal a homogeneous distribution of Co atoms across the C 3 N 4 substrate.…”

“…The isolated atomic dispersion of Co sites is further validated by the atomic line scanning plots (Figure 1d) and three-dimensional surface atom map (Figure 1e). 22 Elemental mapping images of Co 1 /C 3 N 4 reveal a homogeneous distribution of Co atoms across the C 3 N 4 substrate.…”

“…The isolated atomic dispersion of Co sites is further validated by the atomic line scanning plots (Figure 1d) and three-dimensional surface atom map (Figure 1e). 22 Elemental mapping images of Co We conduct density functional theory (DFT) calculations to get insights into the electronic structure of Co 1 /C 3 N 4 . As depicted in Figure S5, the charge density analysis of the Co 1 − N 2 unit reveals a significant electronic coupling between Co 1 and N 2 , with Co 1 contributing remarkable −0.93 |e| electrons to N 2 species.…”

“…Hence, NO 2 RR offers a feasible approach to attain sustainable NH 3 production while concurrently mitigating detrimental NO 2 – emissions. − However, the NO 2 RR process is impeded by the complicated NO 2 – → NH 3 process and competitive HER. To attain a high-efficiency NO 2 RR, the design of high-performance catalysts to promote the NO 2 RR while inhibiting the HER is highly desirable. − …”

Promoting Nitrite-to-Ammonia Electroreduction over Amorphous CoS2 Nanorods

“…We then explore the entire NO 2 – -to-NH 3 reaction pathway to examine the reaction energies of CoS 2 and a-CoS 2 (Figures S10 and S11). According to the previous theoretical studies, − the NO 2 RR generally proceeds via a pathway of *NO 2 → *NO 2 H → *NO → *NHO → *NH 2 O → *NH 2 OH → *NH 2 → *NH 3 . We can see from Figure c that the free energies of all reaction intermediates on CoS 2 are more positive than those on a-CoS 2 .…”