First-Principles Study On Electrocatalytic Oxygen Evolution Reaction Of M₃²⁺N³⁺ Hydrotalcite-Like Compounds

Layered double hydroxides（LDHs）materials have been widely used in the fields of catalysis and adsorption due to their structural characteristics such as adjustable composition of metal ions in the main layer and adjustable type and quantity of interlayer anions.Electrocatalytic oxygen evolution reaction（OER）is an important type of electrocatalytic reaction,and the electrocatalytic OER reaction of hydrotalcite is widely studied.However,the research on the reaction mechanism and regulation of hydrotalcite electrocatalytic OER is not clear.In this paper,the first-principles method is used to systematically study the electrocatalytic OER reaction mechanism of hydrotalcite,the crystal plane effect of hydrotalcite and the regulation of lamellar metal ions.The main contents include the following:1.A series of M₃²⁺N³⁺-LDHs(M²⁺=Co²⁺,Ni²⁺,Zn²⁺,Mg²⁺,Ca²⁺;N³⁺=Co³⁺,Fe³⁺,Cr³⁺,Mn³⁺)were systematically studied by first-principles method.The OER reaction mechanism of three kinds of active sites（*M-M₃N-LDH（110）,*N-M₃N-LDH（110）and*M（M）-M₃N-LDH（110））on the M₃²⁺N³⁺-LDH（110）crystal plane and the regulation of metal ions were discussed.The volcano plot relationship between the OER catalytic activity of M₃²⁺N³⁺-LDHs material andΔG_*O-ΔG_*OH(the adsorption free energy ofΔG_*O:*O intermediate,the adsorption free energy ofΔG_*OH:*OH intermediate)was constructed.The calculated results show that*Co-Co₃Fe-LDH（110）in Co₃Fe-LDH（110）,*Fe-Ni₃Fe-LDH（110）in Ni₃Fe-LDH（110）,*Mn-Ni₃Mn-LDH（110）and*Ni（Ni）-Ni₃Mn-LDH（110）in Ni₃Mn-LDH（110）have potential excellent electrocatalytic OER reactivity.In addition,the results also show that the decrease of band gap of LDH catalyst can promote its electrocatalytic OER activity.For the LDHs catalytic system containing the outer 3d electron,the OER catalytic activity of the（110）crystal plane has a good volcanic diagram relationship with its d-band center.2.The electrocatalytic OER reactivity of different active sites on the（001）,（100）and（110）crystal planes of Ni₃Fe,Co₃Fe and Ni₃Mn-LDH was studied by first-principles method.The calculation results show that the（110）crystal plane has very good electrocatalytic OER reactivity,followed by the（100）crystal plane and the（001）crystal plane.The best active sites*Fe-Ni₃Fe-LDH（110）,*Co-Co₃Fe-LDH（110）,*Mn-Ni₃Mn-LDH（110）and*Ni（Ni）-Ni₃Mn-LDH（110）on the（110）crystal plane are all near the peak position of the electrocatalytic OER volcano plots of Ni₃Fe-LDH,Co₃Fe-LDH and Ni₃Mn-LDH,with smaller overpotential and better OER activity.The density of states analysis shows that the decrease of the band gap of the（001）,（100）and（110）crystal planes of Ni₃Fe-LDH,Co₃Fe-LDH and Ni₃Mn-LDH could promote electron transport.The overpotential（η）of the electrocatalytic OER reaction of the catalyst is small,and the energy of the d-band center is closer to the Fermi level.3.The effect of divalent and trivalent(M^II/M^III)post-transition metal(M^II/M^III=Ru,Rh,Pd,Os,Ir,Pt)doped Co₃Fe-LDH（110）(M^II/M^IIICo₃Fe-LDH（110）)on its electrocatalytic OER activity was studied by first-principles method.The calculation results show that Rh^III and Ir^III doping in Co₃Fe-LDH（110）could promote the electrocatalytic OER activity of Co₃Fe-LDH（110）,and the reaction overpotentials（η）are 0.178 and 0.167 V,respectively.The formed Rh^IIICo₃Fe-LDH（110）and Ir^IIICo₃Fe-LDH（110）have good electrocatalytic OER activity.In addition,the doping effects of divalent M^II and trivalent M^III of the same metal M（M=Ru,Rh,Pd,Os,Ir,Pt）doped into Co₃Fe-LDH（110）were studied.The calculation results show that the d-band center of M^III doped Co₃Fe-LDH（110）catalyst is negatively correlated withη,while the d-band center of M^II doped Co₃Fe-LDH（110）catalyst is positively correlated withη.This shows that the doping of metal ions with different valence states has different doping effects on the electrocatalytic activity of LDH,and its d-band center has a good volcanic diagram relationship withη.