The
ambient electrocatalytic N2 reduction reaction (NRR)
is a promising alternative to the Haber–Bosch process for producing
NH3. However, a guideless search for single-atom-based
and other electrocatalysts cannot promote the NH3 yield
rates by NRR efficiently. Herein, our first-principles calculations
reveal that the successive emergence of vertical end-on *N2 and oblique end-on *NNH admolecules on single metal sites is key
to high-performance NRR. By targeting the admolecules, single Ag sites
with the Ag–N4 coordination are found and synthesized
massively. They exhibit a record-high NH3 yield rate (270.9
μg h–1 mgcat.
–1 or 69.4 mg h–1 mgAg
–1) and a desirable Faradaic efficiency (21.9%) in HCl aqueous solution
under ambient conditions. The generation rate of NH3 is
stable during 20 consecutive reaction cycles, and the reduction current
density is almost constant for 60 h. This work provides an effective
targeting-design principle to purposefully synthesize active and durable
single-atom-based NRR electrocatalysts.
Exploration of efficient catalysts is a priority for the electrochemical nitrogen reduction reaction (NRR) under ambient temperature and pressure. Recently, several nanostructured gold (Au) catalysts have shown impressive catalytic activities toward NRR. However, the atomic origin of high catalytic activities of Au catalysts is vague. In this work, a quantitative relationship between the generalized coordination number (GCN) and NRR activity is established. In particular, the NRR activity is linearly increased with the decrease of GCN values of Au surface atoms. As a proof-of-concept experiment, the NRR activity of nanoporous gold (NPG) with a high proportion of low-coordinated surface atoms is investigated and compared with that of Au octahedra (OCTA) enclosed with (111) facets. As expected, NPG exhibits a high NH 3 production rate of 30.5 μg h −1 mg −1 , which is 5.8 times larger than that of Au OCTA. In addition, the excellent catalytic performance of NPG can be retained for 21 h by showing constant current density, NH 3 production rate, and faradaic efficiency. The findings in this work would provide guiding principles for designing efficient NRR catalysts.
We present a directed graph-based method for distribution network reconfiguration considering distributed generation. Two reconfiguration situations are considered: operation mode adjustment with the objective of minimizing active power loss (situation I) and service restoration with the objective of maximizing loads restored (situation II). These two situations are modeled as a mixed integer quadratic programming problem and a mixed integer linear programming problem, respectively. The properties of the distribution network with distributed generation considered are reflected as the structure model and the constraints described by directed graph. More specifically, the concepts of ''in-degree'' and ''out-degree'' are presented to ensure the radial structure of the distribution network, and the concepts of ''virtual node'' and ''virtual demand'' are developed to ensure the connectivity of charged nodes in every independent power supply area. The validity and effectiveness of the proposed method are verified by test results of an IEEE 33-bus system and a 5-feeder system.
Using hydrazine oxidation reaction (HzOR) to replace the oxygen evolution reaction is an effective way to decrease the overpotential of the anodic reaction in overall water splitting (OWS), facilitating cost‐effective and safe hydrogen production. Herein, Rh2S3/N‐doped carbon hybrids (Rh2S3/NC) are first reported as novel and efficient bifunctional electrocatalysts for hydrazine‐assisted hydrogen generation over a wide pH range. Specifically, Rh2S3/NC exhibits low overpotentials for the hydrogen evolution reaction (HER) in alkaline (38 mV), neutral (46 mV), and acidic (21 mV) electrolytes, to reach the current density of 10 mA cm−2, and maintains the activities over 70 h. Meanwhile, Rh2S3/NC also displays competitive HzOR performance at all‐pH electrolytes. Thus, serving as a bifunctional electrocatalyst for both HER and HzOR, Rh2S3/NC shows overwhelming‐Pt/C performance in three electrolytes, and can save over 93.3%, 85.2%, and 78.3% energy consumption compared to the corresponding OWS system. Moreover, theoretical calculations confirm that Rh2S3/NC owns low free‐energy changes of the H adsorption and the dehydrogenation of adsorbed NHNH both of which are beneficial to enhance catalytic activity. This work develops a novel bifunctional electrocatalyst with free pH‐dependent condition for the hydrazine‐assisted electrolysis system to furtherly reduce the cost of massive industrial H2 production.
Exploration of efficient catalysts is a priority for the electrochemical nitrogen reduction reaction (NRR) in order to receive a high product yield rate and faradaic efficiency of NH3, under ambient conditions. In the present contribution, the binding free energy of N2, NNH, and NH2 were used as descriptors to screen the potential NRR electrocatalyst among different single or binuclear transition metal atoms on N-doped nanoporous graphene. Results showed that the binuclear Mo catalyst might exhibit the highest catalytic activity. Further free energy profiles confirmed that binuclear Mo catalysts possess the lowest potential determining step (hydrogenation of NH2* to NH3). The improved activities could be ascribed to a down-shift of the density of states for Mo atoms. This investigation could contribute to the design of a highly active NRR electrocatalyst.
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