Abstract：
Catalytic conversion of carbon dioxide (CO2) into value-added chemicals is of pivotal importance, well the cost of capturing CO2 from dilute atmosphere is super challenge. One promising strategy is combining the adsorption and transformation at one step, such as applying alkali solution that could selectively reduce carbonate (CO32-) as consequences of CO2 adsorption. Due to complexity of this system, the mechanistic details on controlling the hydrogenation have not been investigated in depth. Herein, Ru/TiO2 catalyst was applied as a probe to elucidate the mechanism of CO32- activation, in which with thermodynamic and kinetic investigations, a compact Langmuir-Hinshelwood reaction model was established which suggests that the overall rate of CO32- hydrogenation was controlled by a specific C-O bond rupture elementary step within HCOO- and the Ru surface was mainly covered by CO32- or HCOO- at independent conditions. This assumption was further supported by negligible kinetic isotope effects (kH/kD ≈ 1), similarity on reaction barriers of CO32- and HCOO- hydrogenation (ΔH‡hydr,Na2CO3 and ΔH‡hydr,HCOONa) and a non-variation of entropy (ΔS‡hydr ≈ 0). More interestingly, the alkalinity of the solution is certainly like a two sides in a sword and could facilitate the adsorption of CO2 while hold back catalysis during CO32- hydrogenation.
摘要：
将二氧化碳（CO2）催化转化为增值化学品至关重要，从稀薄大气中捕获二氧化碳的成本是巨大的挑战。一种有前途的策略是将吸附和转化一步结合起来，例如应用碱性溶液，可以选择性地减少碳酸盐（CO32-）作为CO2吸附的后果。由于这个系统的复杂性,控制氢化的机理细节尚未深入研究。在这里，以Ru/TiO2催化剂为探针,阐明了CO32-活化机理,其中通过热力学和动力学研究，建立了紧凑的Langmuir-Hinshelwood反应模型，该模型表明CO32-氢化的总体速率受HCOO-内特定的C-O键断裂基本步骤控制，Ru表面主要被CO32-或HCOO-覆盖在独立条件下。这一假设得到了可忽略的动力学同位素效应(kH/kD≈1)的进一步支持，CO32-和HCOO-氢化反应势垒的相似性(ΔH®hydr，Na2CO3和ΔH288hydr，HCOONa）和熵的非变化（ΔS288hydr≈0）。更有趣的是，溶液的碱度肯定像剑中的两面，可以促进CO2的吸附，同时在CO32-加氢过程中抑制催化。
