Electrochemical CO₂ reduction (CO₂R) to formate is an attractive carbon emissions mitigation strategy due to the existing market and attractive price for formic acid. Tin is an effective electrocatalyst for CO₂R to formate, but the underlying reaction mechanism and whether the active phase of tin is metallic or oxidized during reduction is openly debated. In this report, we used grand-canonical density functional theory and attenuated total reflection surface-enhanced infrared absorption spectroscopy to identify differences in the vibrational signatures of surface species during CO₂R on fully metallic and oxidized tin surfaces. Our results show that CO₂R is feasible on both metallic and oxidized tin. We propose that the key difference between each surface termination is that CO₂R catalyzed by metallic tin surfaces is limited by the electrochemical activation of CO₂, whereas CO₂R catalyzed by oxidized tin surfaces is limited by the slow reductive desorption of formate. While the exact degree of oxidation of tin surfaces during CO₂R is unlikely to be either fully metallic or fully oxidized, this study highlights the limiting behavior of these two surfaces and lays out the key features of each that our results predict will promote rapid CO₂R catalysis. Additionally, we highlight the power of integrating high-fidelity quantum mechanical modeling and spectroscopic measurements to elucidate intricate electrocatalytic reaction pathways.

中文翻译：

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使用大正则 DFT 和原位 ATR-SEIRA 光谱深入了解金属锡和氧化锡的电化学 CO2 还原

由于甲酸的现有市场和有吸引力的价格，电化学CO ₂还原(CO _{2 R)生成甲酸盐是一种有吸引力的碳排放缓解策略。锡是CO 2} R形成的有效电催化剂，但其基本反应机制以及锡的活性相在还原过程中是金属相还是氧化相仍存在公开争论。在本报告中，我们使用大正则密度泛函理论和衰减全反射表面增强红外吸收光谱来识别全金属和氧化锡表面上CO ₂ R 过程中表面物种振动特征的差异。我们的结果表明CO ₂ R 对于金属锡和氧化锡都是可行的。我们认为，每个表面终止之间的主要区别在于，金属锡表面催化的CO _{2 R 受到CO 2}电化学活化的限制，而氧化锡表面催化的CO ₂ R 受到甲酸盐的缓慢还原解吸的限制。虽然 CO ₂ R过程中锡表面氧化的确切程度不太可能是完全金属化或完全氧化，但这项研究强调了这两个表面的限制行为，并列出了每个表面的关键特征，我们的结果预测这些特征将促进快速 CO _2R催化。此外，我们还强调了集成高保真量子力学建模和光谱测量来阐明复杂的电催化反应途径的力量。