The Oretical Study Of Hcooh Dehydrogenation On Pt/C₂N And Ti/C₂N

Formic acid is a good hydrogen storage material because of its abundant sources,low preparation price,and liquid state at room temperature.At the same time,it can realize the recycling of C1 and have good value for environmental protection.The decomposition of formic acid can occur through a"two-path reaction":H₂and CO₂are generated by dehydrogenation;CO and H₂O are generated by dehydration.The dehydration reaction should be suppressed.Therefore,an excellent catalyst for HCOOH hydrogen production not only has high catalytic activity,but also has good selectivity for dehydrogenation reaction.The modification of catalyst by adjusting the morphology and composition of catalyst or anchoring the metal on an effective carrier not only improve the catalytic activity and selectivity of catalyst,but also increase the utilization rate of the metal and reduce the cost.Carrier also plays an important role in improving the performance of the catalyst.The two-dimensional layered material C₂N obtained by wet chemical synthesis has high conductivity and its uniform cavity structure provides an ideal place for chemical reactions.It is an excellent catalyst substrate material.In this paper,Pt/C₂N and Ti/C₂N are used as the catalysts for dehydrogenation of formic acid,and the decomposition reaction mechanism of formic acid on the catalysts surface is systematically studied by using the density functional theory（DFT）in order to discuss the catalytic activity and selective of the two catalysts.The results show that HCOOH decomposes on the surface of the catalyst Pt/C₂N,Pt and C₂N are activated to form a two-site"synergistic effect",which improves the catalyst activity and promotes the reaction.The dominant path of the decomposition reaction is the formate dehydrogenation path with an energy span only 0.61 eV,and it is much lower than the1.15 eV of the carboxyl dehydrogenation path.At the same time,the aldehyde dehydration path is difficult to occur because HCO and OH intermediates are difficult to co-adsorb stably on the surface of the catalyst.It can be seen that the single-atom catalyst Pt/C₂N as a catalyst for the HCOOH dehydrogenation reaction has the advantages of high metal utilization,good catalytic activity,and excellent selectivity.It has the application potential as a HCOOH dehydrogenation catalyst material.The reaction on the Ti/C₂N surface also has the dual-site"synergistic effect".The energy span of the formate dehydrogenation pathway and the carboxyl dehydrogenation pathway are 0.89 eV and 0.93 eV,respectively.They are competitive relationship.However,the barrier of the carboxyl dehydrogenation pathway is only 0.63 eV,indicating that the decomposition of HCOOH on the Ti/C₂N surface is more likely to occur through the carboxylic acid dehydration reaction pathway,and its catalytic activity for dehydrogenation reaction is better but the selectivity is poor.It is difficult to be used as a catalyst for the decomposition of HCOOH to produce hydrogen,but it has good application prospect as a catalyst for the decomposition of HCOOH.In the different selectivity for the decomposition reaction of formic acid is mainly due to the difference in the way the metal forms the bond with C₂N,in Pt/C₂N and Ti/C₂N.The d_x²-_y²orbitals of Pt combine with the P_xorbital of N atoms in C₂N to form bonds,while the d_xzorbital of Ti atom are hybridized with the largeπbond formed between N and C atoms.This research work can provide basic design ideas and theoretical guidance for the development and improvement of high-efficiency formic acid decomposition hydrogen production catalysts.