Developing highly efficient and cheap catalysts for the CO₂ hydrogenation is the key to achieve CO₂ conversion into clean energy. Herein, periodic density functional theory (DFT) calculations are performed to investigate possible reaction mechanisms for the hydrogenation of CO₂ to formic acid (cis- or trans-HCOOH) product over a single Fe or Ni atom incorporated nitrogen-doped graphene (Fe-N3Gr or Ni-N3Gr) sheets. Our calculations found that the CO₂ hydrogenation proceeds via a coadsorption mechanism to produce cis- or trans-HCOOH over Fe-N3Gr and Ni-N3Gr surfaces, which is classified into 2 steps: (1) the CO₂ hydrogenation to form a formate (HCOO*) intermediate and (2) hydrogen abstraction to produce cis- or trans-HCOOH. The formation of trans-HCOOH over both Fe-N3Gr and Ni-N3Gr surfaces exhibit the obvious superiority due to the low barrier all through the whole channel. The highest energy barriers (E_a) in the case of trans-HCOOH formation on Fe-N3Gr and Ni-N3Gr surfaces are only 0.57 and 0.37 eV, respectively, which indicated that the CO₂ hydrogenation to trans-HCOOH could be realized over these catalysts at low temperatures, especially the Ni-N3Gr surface. On the other hand, our findings show that the competitive reaction that produces CO and H₂O is almost impossible or extremely difficult to proceeds under ambient conditions due to the large E_a for the formation of these side products. Moreover, the microkinetic modeling of the CO₂ hydrogenation on both surfaces was investigated to confirm these results. Thus, the Fe-N3Gr and Ni-N3Gr catalysts reveal excellent catalytic activity and highly selective for CO₂ hydrogenation to trans-HCOOH. This theoretical investigation not only provides a promising catalyst but also gives a deeper understanding of CO₂ hydrogenation reaction.

开发用于CO ₂加氢的高效，廉价的催化剂是实现CO ₂转化为清洁能源的关键。在此，进行周期性密度泛函理论（DFT）计算以研究在单个掺有氮或掺杂氮的石墨烯（Fe-）上将CO ₂加氢成甲酸（顺式或反式-HCOOH）的可能反应机理。N3Gr或Ni-N3Gr）薄板。我们的计算发现，CO _2的氢化反应是通过共吸附机制在Fe-N3Gr和Ni-N3Gr表面上产生顺式或反式HCOOH的过程，该过程分为2个步骤：（1）CO ₂氢化形成甲酸酯（HCOO *）中间体，（2）夺氢生成顺式或反式HCOOH。在Fe-N3Gr和Ni-N3Gr表面上形成反式HCOOH表现出明显的优越性，这是由于贯穿整个通道的低势垒所致。在Fe-N3Gr和Ni-N3Gr表面上形成反式HCOOH时，最高能垒（E _a）分别仅为0.57和0.37 eV，这表明在这些条件下可以实现CO ₂加氢成反式HCOOH催化剂在低温下，尤其是Ni-N3Gr表面。另一方面，我们的发现表明产生CO和H的竞争反应由于形成这些副产物的E _a大，因此在环境条件下几乎不可能或很难进行₂ O的反应。此外，研究了两个表面上CO ₂加氢的微观动力学模型，以证实这些结果。因此，Fe-N3Gr和Ni-N3Gr催化剂显示出优异的催化活性，并且对CO ₂加氢成反式HCOOH具有高度选择性。这一理论研究不仅提供了有希望的催化剂，而且使人们对CO ₂加氢反应有了更深入的了解。