Guzmán Hilmar, Salomone Fabio, Bensaid Samir, Castellino Micaela, Russo Nunzio, Hernández Simelys
CREST Group, Department of Applied Science and Technology (DISAT), Politecnico di Torino, C.so Duca degli Abruzzi, 24, 10129 Turin, Italy.
IIT─Istituto Italiano di Tecnologia, Via Livorno, 60, 10144 Turin, Italy.
ACS Appl Mater Interfaces. 2022 Jan 12;14(1):517-530. doi: 10.1021/acsami.1c15871. Epub 2021 Dec 29.
The development of efficient catalysts is one of the main challenges in CO conversion to valuable chemicals and fuels. Herein, inspired by the knowledge of the thermocatalytic (TC) processes, Cu/ZnO and bare Cu catalysts enriched with Cu were studied to convert CO via the electrocatalytic (EC) pathway. Integrating Cu with ZnO (a CO-generation catalyst) is a strategy explored in the EC CO reduction to reduce the kinetic barrier and enhance C-C coupling to obtain C chemicals and energy carriers. Herein, ethanol was produced with the Cu/ZnO catalyst, reaching a productivity of about 5.27 mmol·g·h in a liquid-phase configuration at ambient conditions. In contrast, bare copper preferentially produced C products like formate and methanol. During CO hydrogenation, a methanol selectivity close to 100% was achieved with the Cu/ZnO catalysts at 200 °C, a value that decreased at higher temperatures (i.e., 23% at 300 °C) because of thermodynamic limitations. The methanol productivity increased to approximately 1.4 mmol·g·h at 300 °C. Ex situ characterizations after testing confirmed the potential of adding ZnO in Cu-based materials to stabilize the Cu/Cu interface at the electrocatalyst surface because of Zn and O enrichment by an amorphous zinc oxide matrix; while in the TC process, Cu and crystalline ZnO prevailed under CO hydrogenation conditions. It is envisioned that the lower *CO binding energy at the Cu catalyst surface in the TC process than in the Cu present in the EC one leads to preferential CO and methanol production in the TC system. Instead, our EC results revealed that an optimum local CO production at the ZnO surface in tandem with a high amount of superficial Cu + Cu species induces ethanol formation by ensuring an appropriate local amount of *CO intermediates and their further dimerization to generate C products. Optimizing the ZnO loading on Cu is proposed to tune the catalyst surface properties and the formation of more reduced CO conversion products.
开发高效催化剂是将一氧化碳转化为有价值的化学品和燃料的主要挑战之一。在此,受热催化(TC)过程知识的启发,研究了富含铜的Cu/ZnO和裸铜催化剂,以通过电催化(EC)途径转化一氧化碳。将铜与ZnO(一种一氧化碳生成催化剂)结合是在EC一氧化碳还原中探索的一种策略,以降低动力学势垒并增强碳-碳偶联,从而获得含碳化学品和能量载体。在此,使用Cu/ZnO催化剂生产乙醇,在环境条件下的液相配置中达到了约5.27 mmol·g⁻¹·h的生产率。相比之下,裸铜优先生成甲酸盐和甲醇等含碳产物。在一氧化碳加氢过程中,Cu/ZnO催化剂在200°C时实现了接近100%的甲醇选择性,由于热力学限制,该值在较高温度下降低(即300°C时为23%)。甲醇生产率在300°C时提高到约1.4 mmol·g⁻¹·h。测试后的非原位表征证实了在铜基材料中添加ZnO的潜力,由于非晶态氧化锌基质使锌和氧富集,从而稳定了电催化剂表面的Cu/Cu界面;而在TC过程中,在一氧化碳加氢条件下,铜和结晶ZnO占主导地位。可以设想,TC过程中铜催化剂表面的CO结合能低于EC过程中铜表面的CO结合能,导致TC系统中优先生成一氧化碳和甲醇。相反,我们的EC结果表明,ZnO表面的最佳局部一氧化碳生成与大量表面Cu⁺Cu物种相结合,通过确保适当的局部*CO中间体数量及其进一步二聚化以生成含碳产物,从而诱导乙醇形成。建议优化铜上的ZnO负载量,以调节催化剂表面性质并形成更多还原的一氧化碳转化产物。