Single Ni supported on Ti3C2O2 for uninterrupted CO2 catalytic hydrogenation to formic acid: A DFT study

Catalytic hydrogenation of carbon dioxide to formic acid (CO2 + H-2 -> HCOOH) is considered as promising strategy for CO2 fixation and recycling utilization. Supported single metal atom exhibits exceptional activity resulted from its unique local chemical environment. In this work, single Ni atom immobilized on O-vacancy defected Ti3C2O2 (Ni@Ti3C2O2) is investigated for CO2 hydrogenation to HCOOH by first principles calculations. Results show that Ni atom can be steadily immobilized on Ti3C2O2, while CO2 catalytic hydrogenation to HCOOH is favorable with a small energy barrier of 0.54 eV via ER mechanism through HCOO intermediate. Importantly, the hydrogenation process could be occurred uninterruptedly. The as-generated HCOOH will be rapidly released during the subsequent CO2 hydrogenation process owning to the lowest desorption barrier of 0.12 eV, which will not restrict the overall catalytic hydrogenation efficiency. Moreover, the large barrier of side reactions, such as C-C coupling, dehydmxylation and further hydrogenation suggests the high selectivity of CO2 hydrogenation to HCOOH. These findings improve our understanding of CO2 hydrogenation mechanism over supported single atom catalysts, and provide a potential platform for CO2 fixation.