氧氮化钒作为稳定的催化剂，用于将氮电化学还原为氨：氧的作用,Journal of Materials Chemistry A

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氧氮化钒作为稳定的催化剂，用于将氮电化学还原为氨：氧的作用
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-11-02 , DOI: 10.1039/d0ta08313e
Jaysree Pan _{1,

2,

3} , Heine Anton Hansen _{1,

2,

3} , Tejs Vegge _{1,

2,

3}

Affiliation

将氮电化学还原为氨可以潜在地利用依赖于可再生能源的小型分散式装置代替基于集中化石燃料的哈伯-博世现有工艺，从而支持可持续的食品和能源基础设施。在用于该反应的过渡金属氮化物电催化剂的开发中的最新活动已显示出希望，但是氧氮化物仍未开发。我们已经对高度有前途的氧氮化钒（VON）进行了严格的计算研究，以首次确定氧氮化物中的氮还原途径以及混合阴离子的作用，这些作用可改善活性表面态，活性，和析氢的选择性。在低氧含量下，电催化性能得到最佳增强（12。₂在N空位处的吸附，而较高的含氧量VON（31.25％）在阴离子空位上显示出最低的N₂吸附/离解势垒（〜0.3 eV），并且也可能是具有较高NH的潜在N₂ RR催化剂_3次翻转频率，尽管与x = 12.5％相比，稳定性较低，且超电势较高（0.6 V-RHE）。由于高度有利的N₂吸收，混合价阴离子，大的动力学势垒和O * / OH * / H *阻止了关键的N空位活性位点自self灭。

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Vanadium oxynitrides as stable catalysts for electrochemical reduction of nitrogen to ammonia: the role of oxygen

Electrochemical reduction of nitrogen to ammonia can potentially replace the existing centralized fossil fuel-based Haber–Bosch process with small, decentralized units relying on electrical energy from renewable sources, thus supporting a sustainable food and energy infrastructure. Recent activities in the development of transition metal nitride electrocatalysts for this reaction have shown promise, but oxynitrides remain unexplored. We have performed a rigorous computational study of the highly promising vanadium oxynitride (VON) to establish for the first time the nitrogen reduction pathway in oxynitrides and the role of the mixed anions that can lead to improved stability of the active surface-states, activity, and selectivity over hydrogen evolution. The electrocatalytic properties are best enhanced at low oxygen content (12.5%) due to optimal balance between consecutive protonation preference at N-sites over V-sites, low onset potential (0.4 V-RHE), and facile N₂ adsorption at N-vacancy sites, while a higher oxygen containing VON (31.25%) shows the lowest N₂ adsorption/dissociation barrier (∼0.3 eV) on the anion vacancy and can also be a potential N₂RR catalyst with a higher NH₃ turn over frequency, albeit with a lower stability and higher overpotential (0.6 V-RHE) compared to x = 12.5%. The critical N-vacancy active sites are protected from self-annihilation by the mixed-valency anions, large kinetic barriers, and site blocking by O*/OH*/H* due to highly favorable N₂ absorption.

更新日期：2020-11-12

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