High overpotentials and low faradic efficiencies plague metal catalysts for direct conversion of CO₂ to methanol and other liquid fuels. RuO₂-based electrocatalysts have been observed to evolve methanol at low overpotentials, which has been attributed to an alternative reaction mechanism with oxygen-coordinated intermediates that can circumvent the limitations imposed by the scaling relations on metal catalysts. Here, we introduce an innovative concept of ligand effects in oxide catalysts. Both IrO₂ and RuO₂ binds OH* and other intermediates from the electrochemical reduction of CO₂ (CO2RR) strongly, but the stable and miscible system Ir_xRu_(1-x)O₂ exhibits anomalous weaker binding energy in the presence of CO* spectators, because of Ru–Ir ligand effects. The weakened adsorbate binding leads to a very low CO2RR onset potential (methanol evolution at −0.2 V RHE). An Ir atom at the bridge site with Ru neighbors binds intermediates such as OH* and OCHO* much weaker, because of synergistic ligand effects and adsorbate–adsorbate interactions. Consequently, a RuO₂ surface doped with Ir move close to the top of the predicted CO2RR volcano for oxides, which offers a significant improvement over state-of-the-art electrocatalysts for conversion of CO₂ into methanol. Analysis of electronic structure parameters with adsorbate binding energies indicates the ligand effect depletes electrons from the Ir atom and shifts the t_2g orbitals. The lack of electron donation from CO* spectators to Ir at the active site cause favorable adsorbate binding.

中文翻译：

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Ir _x Ru _{（1– x）} O ₂（110）表面上的CO ₂电化学还原

高过电势和低法拉第效率困扰着金属催化剂，这些催化剂将CO ₂直接转化为甲醇和其他液体燃料。已经观察到基于RuO ₂的电催化剂在低的超电势下释放出甲醇，这归因于具有氧配位中间体的替代反应机理，该机理可以规避金属催化剂上结垢关系所施加的限制。在这里，我们介绍了氧化物催化剂中配体效应的创新概念。IrO ₂和RuO _2都牢固地结合OH *和来自电化学还原CO ₂（CO2RR）的其他中间体，但是稳定且可混溶的系统Ir _x Ru _（1-x） O₂由于Ru–Ir配体效应，在CO *旁观者的存在下表现出异常弱的结合能。减弱的吸附物结合导致非常低的CO2RR起始电位（甲醇在-0.2 V RHE处放出）。由于与配体的协同作用和吸附物-吸附物的相互作用，与Ru相邻的桥位处的Ir原子与OH *和OCHO *等中间体的结合要弱得多。因此，掺有Ir的RuO ₂表面接近氧化物预测的CO2RR火山的顶部，这相对于将CO ₂转化为甲醇的最先进的电催化剂而言，具有显着的改进。具有吸附质结合能的电子结构参数分析表明，配体效应耗尽了Ir原子中的电子并移动了t_2g轨道。在活性位点，CO *观众缺乏向Ir的电子给体，导致了良好的吸附物结合。