Edge engineering on layered WS₂ toward the electrocatalytic reduction of CO₂: a first principles study

Transition-metal dichalcogenides (TMDCs) have been modified to show excellent electrocatalytic performance for the CO₂ reduction reaction (CO₂RR). However, little research has been reported on the edge modification of WS₂ and its electrocatalytic CO₂RR. In this work, the edge structure of WS₂ with W atoms exposed in the top layer was established by density functional theory calculations. Through using WS₂-xTM-y (x = 1, 2 or 3; y = 1 or 2; TM = Zn, Fe, Co or Ni) models by doping TM atoms on the top layer of WS₂, the effects of dopant species, doping concentration and adsorption sites on their electrocatalytic activity were investigated. Among the models, the active site for the CO₂RR is the W atoms. The doping of TM atoms would affect the bond strength between W and S atoms. After the doping of TM atoms in WS₂-2TM-1 ones, the electrical conduction of S atoms and the underlying W atoms can greatly be improved. Thus the catalytic activities can be significantly increased, in which the WS₂-2Zn-1 model shows the best catalytic activity. The limiting potential (U_L) of the CO₂RR to CO on the WS₂-2Zn-1 model is -0.51 V and the Gibbs energy change (ΔG) for the adsorption of intermediates on the WS₂-2Zn-1 model is ΔG(COOH*) = -0.37 and ΔG(CO*) = -0.51 eV, respectively. Solvation correction showed that WS₂-2Zn-1 could maintain good catalytic performance in a wide range of pH values. The present results may provide a theoretical basis for the design and synthesis of novel electrocatalysts with high performance for the CO₂RR.