Study On Catalyzed Oxidation Process Of H₂PO₂^- And HCHO On Nickel And Copper Using Density Functional Theory

Hypophosphates?[H₂PO₂]?and formaldehyde?HCHO?are the most typical reductant that is widely used in the Ni-electroless deposition and the Cu-electroless,respectively.In this paper,the adsorption and oxidation characteristics on Ni and Cu for this two classical electroless reductants have been studied by using density functional theory?DFT?and cluster model method.The electroless deposition process is theoretically investigated and the calculated results indicated:1.The most stable configurations of[H₂PO₂]^- and HCHO adsorbed on the two metals are that[H₂PO₂]-is adsorbed on the Ni and Cu by its two oxygen atoms,and HCHO is with its carbon and oxygen atoms,respectively.The adsorption energy of[H₂PO₂]-is larger on Ni than on Cu.The adsorption energy of HCHO has little difference between adsorption on Ni and on Cu.2.The natural bond orbit analysis shows that,the electron-transferred number from[H₂PO₂]-to metal Ni and Cu is more when the[H₂PO₂]-is adsorbed on Ni than on Cu.On the contrary this number from HCHO to metal Ni and Cu is more when the HCHO is adsorbed on Cu than on Ni.These facts forebode that[H₂PO₂]-is easier to be oxidized on Ni than on Cu,but HCHO is easier to be oxidized on Cu than on Ni.3.The oxidation process of this two reductants on metal Ni and Cu was studied.In the case of[H₂PO₂]-oxidizing on the Ni,3-coordination intermediate pathway is the dominant pathway.Moreover 5-coordination intermediate pathway is the dominant pathway on metal Cu.As to HCHO oxidation,3-coordination intermediate pathway is the dominant pathway on both Ni and Cu.4.The energy analysis on the oxidation reaction process shows also that the activation energy of the rate determination step for the oxidation reaction of two reductants is higher without than with metal Ni and Cu.This indicates that the oxidation reaction of this two reductants can be catalyzed by the existence of metal Ni and Cu.5.The oxidation of[H₂PO₂]-has a lower activation energy on Ni than on Cu.Nevertheless the oxidation of HCHO has a lower activation energy on Cu than on Ni.This means that Ni has a better catalytic effect for[H₂PO₂]-oxidation,while Cu has a better catalytic effect for HCHO oxidation.The calculation results shows finally,Ni and Cu have different catalytic effects for the oxidation of two reductants.Ni has a good catalytic effect for the oxidation of[H₂PO₂]-,and Cu has a good catalytic effect for the oxidation of HCHO.These conclusions theoretically explained very well the classical experimental conclusion,i.e.,why[H₂PO₂]-?not HCHO?is a good reductant for the Ni-electroless deposition,and HCHO?not[H₂PO₂]-?is a good reductant for the Cu-electroless deposition.