PdCu Electrocatalysts for Selective Nitrate and Nitrite Reduction to Nitrogen
PdCu Electrocatalysts for Selective Nitrate and Nitrite Reduction to Nitrogen
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DOI：
10.1021/acscatal.2c04841
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发表时间：
2023-01-06
期刊：
影响因子：
12.9
通讯作者：
Hatzell, Marta C.
中科院分区：
文献类型：
--
作者：
Lim, Jeonghoon;Chen, Yu;Hatzell, Marta C.
根据催化剂的选择性，电催化转化废物中的硝酸盐可以实现有效的废物修复(NO3-到N-2)或废物价态(NO3-到NH4+)。钯和铜电催化剂通常表现出理想的硝酸盐和亚硝酸盐结合性能，允许有效地破坏硝酸盐。然而，通过材料设计合理地控制选择性仍然是PdCu电催化剂面临的一个关键挑战。在这里，我们使用电化学欠电位沉积方法来合成具有可控铜表面覆盖率的钯纳米立方体电催化剂(例如，部分和全部铜涂层)。然后，我们研究了NO3-破坏(转化)和NO2-还原反应的可能性。我们发现，部分铜包覆的Pd纳米立方体不仅有效地促进了NO3-的95%的还原，而且在连续20次循环(80h)中以89%的选择性增加了NO2-还原为N-2的选择性。我们还表明，在这些条件下，Pd(100)面上的刻面是暴露的。完全包铜的Pd纳米立方体有效地促进了接近99%的NO3-的还原。完全覆盖铜；然而，防止了Pd(100)表面的暴露，促进了NO2-选择性还原为NH4+，在连续20个循环(80h)中有70%的选择性。密度泛函理论(DFT)计算表明，与Pd(100)表面相比，NO3-和NO2-在Cu(100)表面上的吸附更强，而由NO3-或NO2-还原生成的NO*中间体在Pd表面上的吸附更强。势垒计算表明，NO*可以很容易地从铜区迁移到Pd区，并且在高NO*覆盖率下，Pd上的N-N耦合势垒显著减小。综上所述，这些结果表明，在PdCu电催化剂上观察到的高N-2选择性是由于NO*从铜区溢出到Pd区。
Electrocatalytic conversion of nitrate in waste can enable efficient waste remediation (NO3- to N-2) or waste valorization (NO3- to NH4+) depending on the selectivity of the catalyst. Palladium and copper electrocatalysts typically exhibit ideal nitrate and nitrite binding properties, allowing for effective destruction of nitrate. However, rational steering of selectivity through material design remains a critical challenge for PdCu electrocatalyst. Here, we use the electrochemical underpotential deposition method to synthesize palladium nanocube electrocataysts with controlled copper surface coverage (e.g., partial and full copper coatings). We then examine the potential for NO3- destruction (conversion) and NO2- reduction reaction. We identify that partial copper-coated Pd nanocubes not only effectively facilitate the reduction of 95% of NO3- but also increase the reduction of NO2- to N-2 with 89% selectivity over 20 consecutive cycles (80 h). We also show that under these conditions, the Pd(100) surface facet is exposed. Complete copper-covered Pd nanocubes effectively facilitate the reduction of similar to 99% of NO3-. Complete coverage of copper; however, prevented exposure of Pd(100) surface facet, promoting the selective reduction of NO2- to NH4+ with a 70% selectivity over 20 consecutive cycles (80 h). Density functional theory (DFT) calculations show that NO3- and NO2- adsorb more strongly on the Cu(100) surface compared to the Pd(100) surface, while the NO* intermediate generated from NO3- or NO2- reduction adsorbs more strongly on the Pd surface. Barrier calculations show that NO* can readily migrate from the Cu domain to the Pd domain and that the N-N coupling barrier on Pd is significantly diminished at high NO* coverage. Together, these results suggest that the high N-2 selectivity observed on the PdCu electrocatalyst is caused by the spillover of NO* from the Cu domains to the Pd domains.