Messias Igor, Winkler Manuel E G, Costa Gabriel F, Mariano Thiago, Souza Junior João Batista, Neckel Itamar Tomio, Figueiredo Marta C, Singh Nirala, Nagao Raphael
Institute of Chemistry, University of Campinas, Campinas, SP 13083-862, Brazil.
Center for Innovation on New Energies, University of Campinas, Campinas, SP 13083-084, Brazil.
ACS Appl Energy Mater. 2024 Oct 2;7(19):9034-9044. doi: 10.1021/acsaem.4c02326. eCollection 2024 Oct 14.
Nitrate electroreduction reaction (NORR) to ammonia (NH) still faces fundamental and technological challenges. While Cu-based catalysts have been widely explored, their activity and stability relationship are still not fully understood. Here, we systematically monitored the dynamic alterations in the chemical and morphological characteristics of CuO nanocubes (NCs) during NORR in an alkaline electrolyte. In 1 h of electrolysis from -0.10 to -0.60 V vs RHE, the electrocatalyst achieved the maximum NH faradaic efficiency (FE) and yield rate at -0.3 V (94% and 149 μmol h cm, respectively). Similar efficiency could be found at a lower overpotential (-0.20 V vs RHE) in long-term electrolysis. At -0.20 V vs RHE, the catalyst FE increased from 73% in the first 2 h to ∼90% in 10 h of electrolysis. Electron microscopy revealed the loss of the cubic shape with the formation of sintered domains. Raman, X-ray diffraction (XRD), and Cu K-edge X-ray absorption near-edge spectroscopy (XANES) indicated the reduction of CuO to oxide-derived Cu (OD-Cu). Nevertheless, a remaining CuO phase was noticed after 1 h of electrolysis at -0.3 V vs RHE. This observation indicates that the activity and selectivity of the initially well-defined CuO NCs are not solely dependent on the initial structure. Instead, it underscores the emergence of an OD-Cu-rich surface, evolving from near-surface to underlying layers over time and playing a crucial role in the reaction pathways. By employing differential electrochemical mass spectrometry (DEMS) and Fourier transform infrared spectroscopy (FTIR), we experimentally probed the presence of key intermediates (NO and NHOH) and byproducts of NORR (N and NH ) for NH formation. These results show a complex relationship between activity and stability of the nanostructured CuO oxide catalyst for NORR.
硝酸盐电还原反应（NORR）制氨（NH₃）仍然面临着基础和技术方面的挑战。虽然基于铜的催化剂已被广泛研究，但它们的活性与稳定性之间的关系仍未被完全理解。在此，我们系统地监测了碱性电解质中NORR过程中CuO纳米立方体（NCs）的化学和形态特征的动态变化。在相对于可逆氢电极（RHE）从 -0.10 V至 -0.60 V进行1小时的电解过程中，该电催化剂在 -0.3 V时实现了最大的NH₃法拉第效率（FE）和产率（分别为94%和149 μmol h⁻¹ cm⁻²）。在长期电解中，在较低的过电位（相对于RHE为 -0.20 V）下也能发现类似的效率。在相对于RHE为 -0.20 V时，催化剂的FE从最初2小时的73%增加到电解10小时时的约90%。电子显微镜显示立方形状消失，形成了烧结区域。拉曼光谱、X射线衍射（XRD）和Cu K边X射线吸收近边光谱（XANES）表明CuO还原为氧化物衍生的Cu（OD-Cu）。然而，在相对于RHE为 -0.3 V电解1小时后，仍观察到残留的CuO相。这一观察结果表明，最初定义明确的CuO NCs的活性和选择性并不完全取决于初始结构。相反，它强调了富含OD-Cu的表面的出现，该表面随时间从近表面层向底层演化，并在反应途径中起关键作用。通过采用差分电化学质谱（DEMS）和傅里叶变换红外光谱（FTIR），我们通过实验探测了NORR制NH₃过程中关键中间体（NO₂⁻和NHOH）以及副产物（N₂和NH₄⁺）的存在。这些结果表明了纳米结构的CuO氧化物催化剂在NORR中的活性和稳定性之间的复杂关系。
