Dean James, Yang Yahui, Veser Götz, Mpourmpakis Giannis
Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Phys Chem Chem Phys. 2021 Oct 27;23(41):23748-23757. doi: 10.1039/d1cp02245h.
CuZrO has been hypothesized to be a catalytic material with potential applications for CO reduction. Unfortunately, this material has received limited attention in the literature, and to the best of our knowledge the exact crystal structure is still unknown. To address this challenge, we utilize several different structural prediction techniques in concert, including the Universal Structure Predictor: Evolutionary Xtallography (USPEX), the Materials Project Structure Predictor, and the Open Quantum Materials Database (OQMD). Leveraging these structural prediction techniques in conjunction with Density-Functional Theory (DFT) calculations, we determine a possible structure for CuZrO, which resembles a "sandwich" morphology. Our calculations reveal that this new structure is significantly lower in energy than a previously hypothesized perovskite structure, albeit it still has a thermodynamic preference to decompose into CuO and ZrO. In addition, we experimentally tried to synthesize CuZrO based on literature reports and compared computational to experimental X-ray Diffraction (XRD) patterns confirming that the final product is a mixture of CuO and ZrO. Finally, we conducted a computational surface energetics and CO adsorption study on our discovered sandwich morphology, demonstrating that CO can adsorb and activate on the material. However, these CO adsorption results deviate from previously reported results further confirming that the CuZrO is a metastable form and may not be experimentally accessible as a well-mixed oxide, since phase segregation to CuO and ZrO is preferred. Taken together, our combined computational and experimental study provides evidence that the synthesis of CuZrO is extremely difficult and if this oxide exists, it should have a sandwich-like morphology.
据推测，CuZrO是一种具有CO还原潜在应用的催化材料。不幸的是，这种材料在文献中受到的关注有限，据我们所知，其确切晶体结构仍然未知。为了应对这一挑战，我们协同使用了几种不同的结构预测技术，包括通用结构预测器：进化晶体学（USPEX）、材料项目结构预测器和开放量子材料数据库（OQMD）。结合这些结构预测技术与密度泛函理论（DFT）计算，我们确定了CuZrO的一种可能结构，其类似于“三明治”形态。我们的计算表明，这种新结构的能量比先前假设的钙钛矿结构低得多，尽管它在热力学上仍倾向于分解为CuO和ZrO。此外，我们根据文献报道尝试通过实验合成CuZrO，并将计算得到的X射线衍射（XRD）图谱与实验图谱进行比较，证实最终产物是CuO和ZrO的混合物。最后，我们对发现的三明治形态进行了计算表面能学和CO吸附研究，表明CO可以在该材料上吸附并被激活。然而，这些CO吸附结果与先前报道的结果不同，进一步证实了CuZrO是一种亚稳态形式，可能无法通过实验获得作为一种均匀混合的氧化物，因为它更倾向于相分离为CuO和ZrO。综上所述，我们的计算和实验相结合的研究提供了证据，表明CuZrO的合成极其困难，如果这种氧化物存在，它应该具有类似三明治的形态。
