Urrego-Ortiz Ricardo, Builes Santiago, Illas Francesc, Bromley Stefan T, Figueiredo Marta Costa, Calle-Vallejo Federico
Departament de Ciència de Materials i Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, 08028, Barcelona, Spain.
Nano-Bio Spectroscopy Group and European Theoretical Spectroscopy Facility (ETSF), Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, University of the Basque Country UPV/EHU, Av. Tolosa 72, 20018, San Sebastián, Spain.
Commun Chem. 2023 Sep 13;6(1):196. doi: 10.1038/s42004-023-00990-7.
Co-electrolysis of carbon oxides and nitrogen oxides promise to simultaneously help restore the balance of the C and N cycles while producing valuable chemicals such as urea. However, co-electrolysis processes are still largely inefficient and numerous knowledge voids persist. Here, we provide a solid thermodynamic basis for modelling urea production via co-electrolysis. First, we determine the energetics of aqueous urea produced under electrochemical conditions based on experimental data, which enables an accurate assessment of equilibrium potentials and overpotentials. Next, we use density functional theory (DFT) calculations to model various co-electrolysis reactions producing urea. The calculated reaction free energies deviate significantly from experimental values for well-known GGA, meta-GGA and hybrid functionals. These deviations stem from errors in the DFT-calculated energies of molecular reactants and products. In particular, the error for urea is approximately -0.25 ± 0.10 eV. Finally, we show that all these errors introduce large inconsistencies in the calculated free-energy diagrams of urea production via co-electrolysis, such that gas-phase corrections are strongly advised.
同时电解碳氧化物和氮氧化物有望在生产尿素等有价值化学品的同时，帮助恢复碳循环和氮循环的平衡。然而，同时电解过程在很大程度上仍然效率低下，并且存在许多知识空白。在此，我们为通过同时电解生产尿素的建模提供了坚实的热力学基础。首先，我们基于实验数据确定了电化学条件下生成的尿素水溶液的能量学，这使得能够准确评估平衡电位和过电位。接下来，我们使用密度泛函理论（DFT）计算对各种生成尿素的同时电解反应进行建模。对于著名的广义梯度近似（GGA）、元广义梯度近似（meta-GGA）和杂化泛函，计算得到的反应自由能与实验值有显著偏差。这些偏差源于DFT计算的分子反应物和产物能量中的误差。特别是，尿素的误差约为-0.25±0.10电子伏特。最后，我们表明所有这些误差在通过同时电解生产尿素的计算自由能图中引入了很大的不一致性，因此强烈建议进行气相校正。
