| 摘要: | 二氧化碳還原反應(CO2RR)將化石燃料利用所產生的CO2轉化為可用燃料，可有效降低大氣中的CO2濃度，為能源問題提供了潛在解決方案。然而，CO2RR 面臨高過電位、競爭性析氫反應(HER)的加劇、低催化活性和選擇性，以及對高成本貴金屬催化劑依賴等困難。
在本研究中，通過摻入較經濟實惠的In2O3修飾Ag/C觸媒的表面，製備了具有不同Ag/In原子比(8/2、4/6和2/8)的Agx-Iny/C觸媒。高分辨率透射電子顯微鏡(TEM)顯示In2O3分散在Ag表面上形成核-殼結構。X射線光電子能譜(XPS)進一步證實，In2O3的添加降低了Ag表面的價態，暗示了d-band中心的偏移。線性掃描伏安法(LSV)表明，與Ag/C相比，Agx-Iny/C觸媒在-0.6 ~ -1.0 V vs. RHE (VRHE)的電壓範圍內的電流密度較大(負)且過電位較低，表明 In2O3 的加入增強了觸媒的活性並降低了過電位。特別是，Ag2-In8/C表現出最低的過電位和最大的甲酸分電流密度，表明其活性最高且最有利於CO2RR。X射線吸收光譜(XAS)證實In2O3氧化層在反應過程中阻止了內層Ag的氧化，並且Ag-In之間的交互作用增加了觸媒表面的電子轉移。在CO2RR過程中，Ag8-In2/C觸媒在-0.8 VRHE下實現了91.2%的高CO法拉第效率(FECO)，分電流密度為1.67 mA/cm2。同樣，Ag2-In8/C觸媒在-0.9 VRHE下表現出高的95.5%甲酸法拉第效率 (FEHCOOH)，分電流密度為3.53 mA/cm2。經過7小時的穩定性測試，Ag8-In2/C和Ag2-In8/C分別保持高FECO和FEHCOOH，表明觸媒具有出色的穩定性。本研究通過對結構和電催化特性的綜合分析，揭示了Agx-Iny/C觸媒中In2O3表面在調節中間體結合能方面的關鍵作用，從而提出了一種藉控制組成和電壓以調節CO2RR選擇性的新方法。;Carbon dioxide reduction reaction (CO2RR) offers potential solutions to energy problems by converting CO2 from fossil fuel utilization into usable fuels, effectively mitigating atmospheric CO2 levels. However, CO2RR faces difficulties including high overpotential, intensifying competing hydrogen evolution reaction (HER), low catalytic activity and selectivity, and the reliance on costly and noble catalysts.
In this study, the Agx-Iny/C catalysts with different Ag/In atomic ratios of 8/2, 4/6, and 2/8 were prepared by incorporating cost-effective In2O3 to modify the surface of Ag/C catalysts. High-resolution transmission electron microscopy (TEM) revealed that In2O3 was dispersed on the Ag surface to form a core-shell structure. It was further confirmed by X-ray photoelectron spectroscopy (XPS) that the valence state of Ag surface was reduced by the addition of In2O3, implying the shift of the d-band center. Linear sweep voltammetry (LSV) demonstrated that the current density of Agx-Iny/C catalysts exhibited more larger (negative) values and lower overpotentials compared to Ag/C in the voltage range of -0.6 to -1.0 V vs. RHE (VRHE), indicating that the In2O3 addition enhanced the activity and decreased the overpotentials of the catalysts. Particularly, Ag2-In8/C demonstrated the lowest overpotential and the largest formate partial current density, indicating its highest activity and most favorable for CO2RR. X-ray absorption spectroscopy (XAS) confirmed that the In2O3 oxide layer prevented the oxidation of Ag in the inner layer during the reaction, and the interaction between Ag-In increased the electron transfer on the catalyst surface. During CO2RR, the Ag8-In2/C catalyst achieved a high CO faradaic efficiency (FECO) of 91.2% at -0.8 VRHE with a partial current density of 1.67 mA/cm2. Similarly, the Ag2-In8/C catalyst exhibited and high formate faradaic efficiency (FEHCOOH) of 95.5% at -0.9 VRHE with a partial current density of 3.53 mA/cm2. After a 7-hour stability test, the Ag8-In2/C and Ag2-In8/C remain high FECO and FEHCOOH, respectively, indicating excellent catalyst stability. This study reveals the critical role of In2O3 surface in the Agx-Iny/C catalysts in modulating the binding energy of intermediates through the comprehensive analysis of their structure and electrocatalytic characteristics, revealing a novel approach for the selectivity regulation in CO2RR controlled by compositions and potentials. |
