Role of Electronic Structure on Nitrate Reduction to Ammonium: A Periodic Journey
Role of Electronic Structure on Nitrate Reduction to Ammonium: A Periodic Journey
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DOI：
10.1021/jacs.2c05673
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发表时间：
2022-08-04
影响因子：
15
通讯作者：
Stoerzinger, Kelsey
中科院分区：
文献类型：
--
作者：
Carvalho, O. Quinn;Marks, Rylee;Stoerzinger, Kelsey
电催化是一种很有前途的方法，可以将废弃的硝酸盐转化为氨，并有助于关闭氮循环。这种可再生动力的合成氨工艺从水中获取氢气(而不是热Haber-Bosch工艺中的甲烷)，但需要在催化剂的析氢反应(HER)和硝酸盐还原反应(NO3RR)的活性之间取得微妙的平衡，从而影响法拉第效率(FE)和与其他含氮产品相比对氨/铵的选择性。在中性缓冲介质中，我们测量了一系列过渡金属(TMS；Ti，Fe，Co，Ni，Ni0.68Cu0.32，Cu和Ag)中的铵FeS，范围从3.6+/-6.6%(对Ag)到93.7+/-0.9%(对Co)。为了更好地理解这些竞争反应动力学，我们建立了一个微观动力学模型，该模型捕捉了与电压相关的硝酸盐速率级数，并说明了它的来源是硝酸盐和氢吸附原子(H*)之间的竞争吸附。NO3RRFE可以通过与HER的电子竞争来描述，对于具有高功函数和相应高HER活性的TMS，其Fe急剧下降(例如，Ni)。名义上，随着Tm d带中心能(E-d)接近并克服费米能级(E-F)，氨的选择性增加，但与具有类似E-d的材料相比，Co的选择性特别高。密度泛函理论(DFT)计算表明，Co通过(1)强的亚硝酸盐结合使随后的还原成为可能，(2)促进一氧化氮解离，导致氮吸附原子(N*)选择性地还原为铵，从而最大化了铵的选择性。
Electrocatalysis is a promising approach to convert waste nitrate to ammonia and help close the nitrogen cycle. This renewably powered ammonia production process sources hydrogen from water (as opposed to methane in the thermal Haber-Bosch process) but requires a delicate balance between a catalyst's activity for the hydrogen evolution reaction (HER) and the nitrate reduction reaction (NO3RR), influencing the Faradaic efficiency (FE) and selectivity to ammonia/ammonium over other nitrogen-containing products. We measure ammonium FEs ranging from 3.6 +/- 6.6% (on Ag) to 93.7 +/- 0.9% (on Co) across a range of transition metals (TMs; Ti, Fe, Co, Ni, Ni0.68Cu0.32, Cu, and Ag) in buffered neutral media. To better understand these competing reaction kinetics, we develop a microkinetic model that captures the voltage-dependent nitrate rate order and illustrates its origin as competitive adsorption between nitrate and hydrogen adatoms (H*). NO3RR FE can be described via competition for electrons with the HER, decreasing sharply for TMs with a high work function and a correspondingly high HER activity (e.g., Ni). Ammonium selectivity nominally increases as the TM d-band center energy (E-d) approaches and overcomes the Fermi level (E-F), but is exceptionally high for Co compared to materials with similar E-d. Density functional theory (DFT) calculations indicate Co maximizes ammonium selectivity via (1) strong nitrite binding enabling subsequent reduction and (2) promotion of nitric oxide dissociation, leading to selective reduction of the nitrogen adatom (N*) to ammonium.