Heterostructured Co-Doped-Cu2O/Cu Synergistically Promotes Water Dissociation for Improved Electrochemical Nitrate Reduction to Ammonia.

Electrochemical nitrate reduction reaction (NO3RR) has recently emerged as a promising approach for sustainable ammonia synthesis and wastewater treatment, while the activity and selectivity for ammonia production have remained low. Herein, rational design and controllable synthesis of heterostructured Co-doped Cu2O/Cu nanoparticles embedded in carbon framework (Co-Cu2O/Cu@C) is reported for NO3RR. The Co-Cu2O/Cu@C exhibits a high ammonia yield rate of 37.86 mg h-1 mg-1 cat. with 98.1% Faraday efficiency, which is higher than those obtained for most of the Cu-based catalysts under similar conditions. Density functional theory calculations indicated that the strong electronic interactions at Cu/Co-Cu2O interface facilitate the N species deoxygenation process and doping of Co promotes water dissociation to generate *H for the N species hydrogenation process, leading to enhanced NO3RR performance. This work provides a new design strategy toward high-performance catalysts toward NO3RR for ammonia generation.

Interfacially Engineered Nanoporous Cu/MnOx Hybrids for Highly Efficient Electrochemical Ammonia Synthesis via Nitrate Reduction.

Electrochemical reduction of nitrate to ammonia (NH3 ) not only offers a promising strategy for green NH3 synthesis, but also addresses the environmental issues and balances the perturbed nitrogen cycle. However, current electrocatalytic nitrate reduction processes are still inefficient due to the lack of effective electrocatalysts. Here 3D nanoporous Cu/MnOx hybrids are reported as efficient and durable electrocatalysts for nitrate reduction reaction, achieving the NH3 yield rates of 5.53 and 29.3 mg h-1 mgcat. -1 with 98.2% and 86.2% Faradic efficiency in 0.1 m Na2 SO4 solution with 10 and 100 mm KNO3 , respectively, which are higher than those obtained for most of the reported catalysts under similar conditions. Both the experimental results and density functional theory calculations reveal that the interface effect between Cu/MnOx interface could reduce the free energy of rate determining step and suppress the hydrogen evolution reaction, leading to the enhanced catalytic activity and selectivity. This work provides an approach to design advanced materials for NH3 production via electrochemical nitrate reduction.

The development of catalysts for electrochemical nitrogen reduction toward ammonia: theoretical and experimental advances.

Ammonia (NH3) is essential for the industrial production of fertilizers, pharmaceuticals, plastics, synthetic fibers, resins, and chemicals, and it is also a promising carbon-free energy carrier. The electrocatalytic nitrogen reduction reaction (eNRR) driven by renewable energy sources at ambient temperature and atmospheric pressure is an alternative approach to the Haber-Bosch process for NH3 synthesis. However, the efficient electrocatalytic reduction of nitrogen (N2) to NH3 is challenging due to the lack of effective electrocatalysts. Tremendous effort has been made to develop high-performance electrocatalysts for the eNRR in the past few years. In this review, we summarize recent progress relating to electrocatalysts for the eNRR from both theoretical and experimental aspects. Remaining challenges and perspectives for promoting the eNRR to generate NH3 are also discussed. This review hopes to guide the design and development of efficient electrocatalysts for the eNRR for NH3 synthesis.

Efficient Electrocatalytic Nitrogen Reduction to Ammonia on Ultrafine Sn Nanoparticles.

Electrocatalytic nitrogen reduction reaction (NRR) at ambient conditions is a promising route for ammonia (NH3) synthesis but still suffers from low activity and selectivity. Here, ultrafine Sn nanoparticles (NPs) grown on carbon blacks (SnSC/C) have been synthesized through a wet-chemical method using sodium citrate dehydrate as a stabilizing agent. Benefiting from the small sizes of Sn NPs, the SnSC/C catalyst exhibits excellent electrocatalytic performance for NRR with a high Faradaic efficiency of 22.76% and an NH3 yield rate of 17.28 µg h-1 mg-1 in the 0.1 M Na2SO4 electrolyte, outperforming many reported electrocatalysts for NRR under similar conditions. Density functional theory calculation results reveal that the potential-determining step on Sn NPs is the generation of NHNH* through simultaneous hydrogenation of N2* by a H* and a H+/e- pair via Langmuir-Hinshelwood plus Eley-Rideal mechanisms.

Low-frequency oscillations in coupled phase oscillators with inertia.

This work considers a second-order Kuramoto oscillator network periodically driven at one node to model low-frequency forced oscillations in power grids. The phase fluctuation magnitude at each node and the disturbance propagation in the network are numerically analyzed. The coupling strengths in this work are sufficiently large to ensure the stability of equilibria in the unforced system. It is found that the phase fluctuation is primarily determined by the network structural properties and forcing parameters, not the parameters specific to individual nodes such as power and damping. A new "resonance" phenomenon is observed in which the phase fluctuation magnitudes peak at certain critical coupling strength in the forced system. In the cases of long chain and ring-shaped networks, the Kuramoto model yields an important but somehow counter-intuitive result that the fluctuation magnitude distribution does not necessarily follow a simple attenuating trend along the propagation path and the fluctuation at nodes far from the disturbance source could be stronger than that at the source. These findings are relevant to low-frequency forced oscillations in power grids and will help advance the understanding of their dynamics and mechanisms and improve the detection and mitigation techniques.