The electrochemical nitrogen reduction reaction (NRR) is expected to achieve sustainable ammonia synthesis via direct nitrogen fixation; however, the high-quality catalysts that play a crucial role in the NRR are still lacking. The emerging transition metal−1,3,5-triethynylbenzene (TM-TEB) frameworks offer attractive possibilities in the electrochemical catalysis due to the featured atomic and electronic structures. This work presents a comprehensive first-principles study of the TM-TEB systems for TMs from the first three d-block series and systematically explores their potential applications as NRR electrocatalysts. By designing a hierarchical screening strategy, the TM-TEB systems are evaluated based on the NRR catalytic activity as well as the competition from the hydrogen evolution reaction. In addition, in order to have a deeper understanding of the catalytic activities of the TM-TEB systems, diverse possible NRR paths on the TM-TEB surfaces are completely analyzed as well. Our analysis reveals that the TM-TEB systems with TM = V, Mo, Tc, W, and Os are electrocatalysts with a high NRR catalytic activity, while among them, only Mo-and V-TEB show promising NRR selectively. This work demonstrates the great potential of the TM-TEB systems as electrocatalysts in the NRR process, which improves the understanding of the TM-TEB systems and can motivate further exploration of their application in catalysis.
This work systematically studies the product self-catalysis of in situ electrochemical cobalt doping of Li 2 O 2 and reveals its potential mechanism for improving the performance of lithium−oxygen (Li−O 2 ) batteries. Theoretical calculations demonstrate that the discharge products contain substituted and interstitial Co impurities, which serve as active sites to promote the formation of Li 3 O 4 crystallization, thus switching the nucleation mechanism from the main discharge product Li 2 O 2 to Li 3 O 4 . This Co-doping behavior leads to the thermodynamically favorable and dynamically stable formation of Li 3 O 4 crystals during the discharge process. Through systematic investigation of the structural, energetic, electronic, diffusive, and catalytic properties of the Co-doped Li 2 O 2 and Li 3 O 4 compounds, we found that Li 3 O 4 has better charge/mass transport and a lower overpotential for the Li 3 O 4 formation/ decomposition reaction. Consequently, this work elucidates that Co doping provides a simple and effective approach for increasing the proportion of Li 3 O 4 , which can significantly improve the Li−O 2 battery performance.
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