Theoretical Study On The Performance Of Electrocatalysts For Carbon Dioxide Reduction And Nitrogen Electroreduction

The reclamation and recycling of carbon dioxide?CO₂?is an important and pressing task to curb global warming and thus has a multiple practical significance for energy,environment,and economy.How to design and synthesize electrocatalysts with highly catalytic activity and stable cycle life for CO₂ reduction reaction is an important and difficult issue in this field.Nitrogen fixation,which can convert the abundant dinitrogen?N₂?in the Earth's atmosphere to ammonia?NH₃?,is crucial to sustain all forms of life because nitrogen is required to biosynthesize basic building blocks of plants,animals,and other life forms.In this paper,we mainly studied the TMN₄/graphene as a metal-based CO₂ER electrocatalyst and the possibility of either single transition metal doped,or B-doped C₂N layer be used as potential metal-free electrocatalyst for NRR.The results are shown below:?1?The single Co,Rh,and IrN₄/graphene exhibit superior catalytic activity towards CO₂ reduction.In particular,CH₃OH is the preferred product of CO₂ER on the CoN₄/graphene catalyst with an overpotential of 0.59 V,while the RhN₄/graphene and IrN₄/graphene catalysts prefer to reduce CO₂ to CH₂O with an overpotential of 0.35 and0.29 V,respectively.?2?Mo@C₂N is predicted to exhibit the best catalytic activity among the TM@C₂N,in which the proton-coupled electron transfer of the NH₂^*species to NH₃?g?is the potential-determining step.Especially,the computed onset potential of the NRR on Mo@C₂N is-0.17 V.?3?the B_int-doped C₂N layer can sufficiently activate the N₂ molecule through the“acceptance-donation”process due to its significant positive charge and magmoment on the B dopant.Meanwhile,the subsequent N₂ reduction reaction prefers to proceed via the enzymatic mechanism with a rather low limiting potential?0.15 V?,suggesting its superior catalytic performance for N₂ reduction.the results of this study demonstrate that the TMN₄/graphene is a novel based CO₂RR electrocatalust with high efficiency and tunable activity,a single transition metal?TM?atom supported on the experimentally feasible two-dimensional C₂N monolayer?TM@C₂N?has excellent catalytic activity of NRR.In addition,by carefully controlling the doping sites,the B-doped C₂N layer can be utilized as a quite promising metal-free catalyst with high-efficiency for N₂ reduction.We hope that our studies could inspire more experimental and theoretical studies on developing other kinds of 2D nanomaterials electrocatalysts.