Wu Xuanhao, Nazemi Mohammadreza, Gupta Srishti, Chismar Adam, Hong Kiheon, Jacobs Hunter, Zhang Wenqing, Rigby Kali, Hedtke Tayler, Wang Qingxiao, Stavitski Eli, Wong Michael S, Muhich Christopher, Kim Jae-Hong
Department of Environmental Engineering, Zhejiang University, Hangzhou 310058, China.
Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut 06511, United States.
ACS Catal. 2023 May 3;13(10):6804-6812. doi: 10.1021/acscatal.3c01285. eCollection 2023 May 19.
The occurrence of high concentrations of nitrate in various water resources is a significant environmental and human health threat, demanding effective removal technologies. Single atom alloys (SAAs) have emerged as a promising bimetallic material architecture in various thermocatalytic and electrocatalytic schemes including nitrate reduction reaction (NRR). This study suggests that there exists a stark contrast between thermocatalytic (T-NRR) and electrocatalytic (E-NRR) pathways that resulted in dramatic differences in SAA performances. Among Pd/Cu nanoalloys with varying Pd-Cu ratios from 1:100 to 100:1, Pd/Cu SAA exhibited the greatest activity (TOF = 2 min) and highest N selectivity (94%) for E-NRR, while the same SAA performed poorly for T-NRR as compared to other nanoalloy counterparts. DFT calculations demonstrate that the improved performance and N selectivity of Pd/Cu in E-NRR compared to T-NRR originate from the higher stability of NO* in electrocatalysis and a lower N formation barrier than NH due to localized pH effects and the ability to extract protons from water. This study establishes the performance and mechanistic differences of SAA and nanoalloys for T-NRR versus E-NRR.
各种水资源中高浓度硝酸盐的出现对环境和人类健康构成了重大威胁，需要有效的去除技术。单原子合金（SAA）已成为包括硝酸盐还原反应（NRR）在内的各种热催化和电催化方案中一种有前途的双金属材料结构。本研究表明，热催化（T-NRR）和电催化（E-NRR）途径之间存在鲜明对比，这导致了SAA性能的显著差异。在钯铜比从1:100到100:1变化的钯/铜纳米合金中，钯/铜SAA对E-NRR表现出最大活性（TOF = 2分钟）和最高的氮选择性（94%），而与其他纳米合金相比，相同的SAA在T-NRR中表现不佳。密度泛函理论计算表明，与T-NRR相比，钯/铜在E-NRR中性能和氮选择性的提高源于电催化中NO*的更高稳定性，以及由于局部pH效应和从水中提取质子的能力，导致氮的形成势垒低于氨。本研究确定了SAA和纳米合金在T-NRR与E-NRR中的性能和机理差异。
