第一作者：Kasala Prabhakar Reddy通讯作者：José A. Rodriguez通讯单位：石溪大学 研究背景CO2直接转化为甲醇（CH3OH）是降低人类活动CO2排放的有效途径，且绿色氢气的加入可以提高能效，并使H2以液体甲醇的形式存储与运输。然而，由于CO2的热力学稳定性较高，且容易生成副产物（如CO、CH4），因此选择性转化为甲醇具有挑战性。近年来，铟基催化剂（如In2O3）表现出较高的甲醇选择性（>80%）。铟氧化物催化剂通过表面氧空位促进CO2活化，并稳定甲醇中间体。将金属（如Au）沉积到In2O3上，形成金属-氧化物界面，可以进一步增强CO2转化效率。金属铟合金（如In–Au）和逆反应氧化物/金属催化剂结构（如Au/In2O3）表现出较高的CO2氢化选择性和活性。尽管铟基催化剂的研究已经取得进展，但其催化性质和化学演化仍不完全明了，需要进一步研究金属-氧化物界面在CO2激活和甲醇选择性转化中的作用。 成果简介1. 催化剂特性与反应机制：研究探讨了In/Au(111)合金和InOx/Au(111)反向催化剂在CO2氢化反应中的行为。通过同步辐射环境压力X射线光电子能谱（AP-XPS）和批量反应器催化测试发现，In/Au(111)合金具有较高的CO2活性，能够在室温下断裂CO2分子并生成InOx纳米结构。2. 催化剂性能与选择性：在低浓度的In（≤0.05 ML）时，生成的InOx纳米结构在CO2氢化条件下不稳定，主要产物为CO，且甲醇产率较低。而当In覆盖量增加至0.3 ML时，InOx纳米结构在CO2氢化条件下稳定，催化剂表现出高选择性（约80%）地生成甲醇。3. 催化活性与对比数据：在CO2转化活性方面，InOx/Au(111)催化剂的表现至少是纯In2O3或Cu(111)以及Cu/ZnO(0001̅)基准催化剂的10倍以上。AP-XPS分析表明，InOx/Au(111)催化剂通过甲氧基中间体生成甲醇，为CO2转化为甲醇提供了新的催化路径。 材料制备In–Au(111) 和InOx/Au(111) 表面制备铟（In）和金（Au）可以形成不同成分的合金。之前有研究报道了在300 K下将铟沉积到干净的Au(111)表面上的扫描隧道显微镜（STM）图像。在低铟覆盖度（<0.1 ML）下，铟原子选择性地吸附在Au(111)表面特征性人字形结构的肘部位置，形成0.3–0.5 nm大小的二维（2D）岛状结构，这些岛屿主要位于肘部的边缘。X射线光电子能谱（XPS）测量显示，铟和金原子通过混合形成了表面合金，这与两种金属的高相容性一致。当铟的覆盖度增加到0.1 ML时，出现了有序结构，铟金属从金的肘部生长并向⟨110⟩方向扩展。这表明铟是通过Frank–van
der Merwe模式在金基底上生长的，即吸附原子在基底上形成二维（2D）层。与金（1.185 J m–2）相比，铟的表面自由能较低（0.556 J m–2），这表明铟应该润湿金表面并在水平方向上扩散，而不是形成三维（3D）有序簇或渗入金基底。 文章要点Figure 1. XPS
spectra of Au 4f (a) and In 3d (b) core levels, In MNN Auger (c), and valence
band region (d) for clean Au (111), in black, and surfaces with 0.07 (red),
0.16 (blue) and 0.32 (green) ML of indium. All the XPS spectra were collected
under UHV at 300 K using Al Kα (1486.6 eV) radiation. Figure 2. AP-XPS
spectra for Au(111) surfaces with 0.07 (a,b) and 0.32 ML (c,d) of In collected
under different conditions: as deposited indium at 300 K (bottom, black
traces), under CO2 (40 mTorr) at 300 and 500 K (red and blue traces),
followed by H2 (30 mTorr) exposure at 300 and 500 K (green and purple
traces). All the spectra shown in this figure were acquired using Al Kα (1486.6
eV) radiation. Figure 3. Rates
for CO2 conversion (top) and CH3OH production (bottom) as a function of
indium coverage on Au (111) under 0.5 bar of CO2 + 4.5 bar of H2 at
550 K. For comparison we also show the corresponding results for a thick In2O3–x film
(blue line) in the bottom right side of each plot. Figure 4. Selectivity
for CH3OH production as a function of indium coverage on Au (111) under 0.5 bar
of CO2 + 4.5 bar of H2 at 550 K. For comparison, we also include the
results for a thick In2O3–x film (blue bar) on the right side of the
figure. In these experiments, CO and CH3OH were the only reaction products
detected during the hydrogenation of CO2. Figure 5. In MNN
spectra for 0.05, 0.15, and 0.3 ML of In on Au (111). The spectra were
collected after indium deposition (In–Au(111), black traces), full oxidation
with O2 (In2O3/Au (111), green traces), and after the CO2 hydrogenation
reaction (blue traces). In the second step, each surface was exposed to 10 Torr
of O2 at 550 K for 20 min to induce the full oxidation of the indium
deposited on the gold substrate. After this initial oxidation, the In MNN
spectra match the one reported for bulk In2O3 (Figure S1c). Interaction with the CO2/H2 reaction
mixture induced a complete reduction of the surface with 0.05 ML of indium
oxide. In the case of 0.15 ML of indium oxide, the final In MNN spectrum
contained features that matched those observed for metallic In (in black) and
partially reduced indium oxide (red). The corresponding degree of reduction in
the case of the surface with 0.3 ML of indium oxide was the smallest. All the
spectra shown in this figure were acquired using Mg Kα (1253.6 eV) radiation. Figure 6.Arrhenius plots for CH3OH synthesis on Cu (111), plain In2O3–x and
0.3 ML of InOx on Au(111). In these experiments, all the
catalysts were under 0.5 bar of CO2 + 4.5 bar of H2 at
different temperatures. Figure 7. In-situ
XPS spectra of C 1s and In MNN for the 0.05 ML (a, b) and 0.3 ML (c, d) of
indium deposited on Au (111). In preliminary step, In–Au alloys were exposed to
500 mTorr of O2 at 500 K for 20 min to induce the formation of
InOx/Au(111). The spectra were collected using photon
energies of 470 (C 1s region) and 650 (In MNN region) eV. Figure 8. (a,b)
STM image of an In–Au(111) alloy surface and its catalytic activity. (c,d)
Similar results for a InOx/Au(111) surface. The STM images
were reproduced with permission from reference (29) (Copyright 2020 American Institute of
Physics). The surface shown in (c) undergoes only partial reduction under CO2 hydrogenation
conditions (center panel in Figure 5). 结论与展望在本研究中，我们制备了不同铟覆盖度的In/Au(111)和InOx/Au(111)表面，并通过同步辐射AP-XPS和催化测试研究了它们的行为。结果表明，In–Au(111)合金在与O2或CO2反应时会发生氧化。AP-XPS对预氧化的InOx/Au(111)的研究发现，在CO2氢化过程中，低覆盖度（约0.05 ML）的InOx在500 K以上完全还原，生成表面Au–In金属间合金。这种合金催化剂对CO2转化具有较高活性，但对甲醇的选择性较低（约25%）。进一步增加铟的覆盖度（0.3 ML）后，形成了稳定的反向InOx/Au(111)催化剂。该氧化物-金属界面对CO2转化具有良好的活性，并对甲醇的选择性较高（约80%）。在300 K下，1 Torr CO2 + H2气氛中，C 1s XPS核心谱图显示，InOx/Au(111)表面以碳酸根（CO3*）为主，随着温度升高至500 K，转化为甲酸根（HCOO*）和甲氧基（H3CO*）中间体，这些都是甲醇生成的关键中间体。与基准催化剂如Cu(111)、Cu/ZnO(0001̅)和ZnO/Cu(111)相比，0.3 ML InOx的Au(111)表面在甲醇生产上表现更为优异。因此，含InOx的反向氧化物/金属催化剂为提高CO2选择性转化为甲醇的过程提供了新的可能，尤其在环保和绿色化学领域具有应用前景。文献信息：https://doi.org/10.1021/acscatal.4c05837声明：译文仅供参考，具体细节请读者朋友阅读原始文献。 科学温故QQ群—科研爱好者集中地！（不定期发布讲座通知，分享录制视频）微信群（学术交流/电催化/光催化/理论计算/资源共享/文献互助群；C1化学/生物质/单原子/多孔材料分舵），小编微信：hao-xinghua或alicezhaovip，备注“姓名-单位”。
