B-doped MoS2 for nitrate electroreduction to ammonia.

Electrocatalytic nitrate-to-ammonia conversion (NO3RR) is a promising route to achieve both NH3 electrosynthesis and wastewater treatment. Herein, we report B-doped MoS2 nanosheet arrays as an efficient NO3RR catalyst, delivering an NH3-Faradaic efficiency of 92.3 % with the corresponding NH3 yield of 10.8 mg h-1 cm-2 at -0.7 V (RHE). Theoretical computations identify B-dopants as the pivotal active sites to enhance NO3- activation and optimize the free energies of reaction intermediates, leading to the expedited NO3RR activity. Meanwhile, the undesired hydrogen evolution can be well suppressed on B-MoS2 to render a high NO3RR selectivity.

A vacancy engineered MnO2-x electrocatalyst promotes nitrate electroreduction to ammonia.

The NO3- reduction reaction (NO3RR) has recently emerged as a potential approach for sustainable and efficient NH3 production, whereas exploring high-performance NO3RR electrocatalysts is highly desirable yet challenging. Herein, we attempted to construct O-vacancies (OVs) on MnO2 nanosheets and the resulting OV-rich MnO2-x showed a high NH3 yield of 3.34 mg h-1 cm-2 (at -1.0 V vs. RHE) and an excellent FE of 92.4% (at -0.9 V vs. RHE), together with the outstanding stability. DFT calculations reveal that OVs on MnO2 serve as catalytic centers to enhance NO3- adsorption and dissociation, reduce the energy barriers of hydrogenation steps and thus promote NO3--to-NH3 conversion.

Boosted nitrate electroreduction to ammonia on Fe-doped SnS2 nanosheet arrays rich in S-vacancies.

The electrochemical nitrate reduction reaction (NO3RR) not only holds great potential for the removal of NO3- contaminants from the environment, but also potentially provides a renewable-energy-driven NH3 synthesis method to replace the Haber-Bosch process. Herein, we report that Fe-doped SnS2 nanosheets enriched with S-vacancies can be used as an efficient NO3RR catalyst, showing a high NH3 yield of 7.2 mg h-1 cm-2 (at -0.8 V) and a faradaic efficiency of 85.6% (at -0.7 V). Density functional theory (DFT) calculations revealed that S-vacancies on Fe-SnS2 serve as the main active sites for the NO3RR and the Fe-doping can further regulate the electronic structure of S-vacancies to optimize the binding energies of NO3RR intermediates, resulting in reduced energy barriers and enhanced NO3RR activity.

PdFe Single-Atom Alloy Metallene for N2 Electroreduction.

Single-atom alloys hold great promise for electrocatalytic nitrogen reduction reaction (NRR), while the comprehensive experimental/theoretical investigations of SAAs for the NRR are still missing. Herein, PdFe1 single-atom alloy metallene, in which the Fe single atoms are confined on a Pd metallene support, is first developed as an effective and robust NRR electrocatalyst, delivering exceptional NRR performance with an NH3 yield of 111.9 µg h-1 mg-1 , a Faradaic efficiency of 37.8 % at -0.2 V (RHE), as well as a long-term stability for 100 h electrolysis. In-depth mechanistic investigations by theoretical computations and operando X-ray absorption/Raman spectroscopy indentify Pd-coordinated Fe single atoms as active centers to enable efficient N2 activation via N2 -to-Fe σ-donation, reduced protonation energy barriers, suppressed hydrogen evolution and excellent thermodynamic stability, thus accounting for the high activity, selectivity and stability of PdFe1 for the NRR.

High-Efficiency N2 Electroreduction Enabled by Se-Vacancy-Rich WSe2-x in Water-in-Salt Electrolytes.

Electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable NH3 production, while developing the NRR electrocatalysis systems with both high activity and selectivity remains a significant challenge. Herein, we combine catalyst and electrolyte engineering to achieve a high-efficiency NRR enabled by a Se-vacancy-rich WSe2-x catalyst in water-in-salt electrolyte (WISE). Extensive characterizations, theoretical calculations, and in situ X-ray photoelectron/Raman spectroscopy reveal that WISE ensures suppressed H2 evolution, improved N2 affinity on the catalyst surface, as well as an enhanced π-back-donation ability of active sites, thereby promoting both activity and selectivity for the NRR. As a result, an excellent faradaic efficiency of 62.5% and NH3 yield of 181.3 µg h-1 mg-1 is achieved with WSe2-x in 12 m LiClO4, which is among the highest NRR performances reported to date.

MoS2 quantum dots for electrocatalytic N2 reduction.

We demonstrate that MoS2 quantum dots (QDs) can be an effective and durable catalyst for the electrocatalytic N2 reduction reaction (NRR), showing an NH3 yield of 39.6 µg h-1 mg-1 with a faradaic efficiency of 12.9% at -0.3 V, far superior to MoS2 nanosheets and outperforming most reported NRR catalysts. Density functional theory computations unravel that the MoS2 QDs can dramatically facilitate N2 adsorption and activation via side-on patterns, resulting in an energetically-favored enzymatic pathway with an ultra-low overpotential of 0.29 V.

Bimetallic MnMoO4 with dual-active-centers for highly efficient electrochemical N2 fixation.

The nitrogen reduction reaction (NRR) is a key step in electrochemical nitrogen fixation and exploring high-performance electrocatalysts is of paramount significance for achieving the desired NRR efficiency. Herein, we demonstrate that bimetallic MnMoO4 can be a highly active and durable NRR catalyst. The developed MnMoO4 nanorods-reduced graphene oxide presented a favorable combination of both high NH3 yield (60.3 µg h-1 mg-1) and high faradaic efficiency (14.7%), surpassing nearly all of the previously reported Mn and Mo-based NRR catalysts. Theoretical calculations revealed that the surface-terminated Mn and Mo atoms functioned as dual-active-centers to synergistically boost the NRR and suppress the adverse hydrogen evolution.