In heterogeneous catalysis, transformation of CO₂ into formate largely relies on supported palladium catalyst, in which the support and in particular the support basicity plays a critical role. In this study, we prepared a series of Pd catalysts loaded on ZrO₂ bearing three different crystal phases, namely the tetragonal phase (ZrO₂-T), the monoclinic phase (ZrO₂-M), and the hybrid tetragonal and monoclinic phase (ZrO₂-M&T). With the same metal loading, ZrO₂-T supported Pd catalyst exhibited considerably higher intrinsic activity in CO₂ hydrogenation into formate compared with the other two catalysts. Pd/ZrO₂-T with 2 wt% Pd was the most active one in the series, affording a TOF of 2817 h⁻¹ at 373 K. In situ DRIFTS spectroscopy, kinetic study and CO₂-TPD analysis provided evidence that all Pd/ZrO₂ catalysts follow a similar catalytic mechanism, and the origin of the superior activity for Pd/ZrO₂-T is the higher density of weak basic sites on ZrO₂-T, which facilitates the transformation of CO₂ into the desirable surface adsorbed bicarbonate as the precursor for formate. This work highlights the importance of crystal-phase engineering of the support in tuning the catalytic activity of Pd based catalysts for CO₂ hydrogenation.

在非均相催化中，CO ₂转化成甲酸主要依赖于负载的钯催化剂，其中载体尤其是载体的碱度起着至关重要的作用。在这项研究中，我们制备了一系列负载在ZrO ₂上的Pd催化剂，它们具有三个不同的晶相，即四方相（ZrO ₂ -T），单斜晶相（ZrO ₂ -M）以及杂化四方和单斜晶相（ZrO ₂ -M）。 ZrO ₂ -M＆T）。在相同的金属负载下，与其他两种催化剂相比，ZrO ₂ -T负载的Pd催化剂在CO ₂加氢成甲酸中表现出相当高的固有活性。钯/锆₂具有2 wt％Pd的-T是该系列中活性最高的一个，在373 K下的TOF为2817 h ^-1。原位DRIFTS光谱，动力学研究和CO ₂ -TPD分析提供了所有Pd / ZrO ₂催化剂的证据。遵循相似的催化机制，以及用于钯/的ZrO优越活性的起源₂ -T是弱碱性部位上的ZrO高密度₂ -T，这有利于CO转化₂到所需的表面吸附的碳酸氢盐作为前体争取 这项工作强调了载体的晶相工程在调节Pd基催化剂对CO ₂加氢的催化活性方面的重要性。