Preparation Of Morphology-controllable Bi₂O₃ Nanomaterials And Composites And Study Of Their CO₂ Electroreduction Performanc

Electrocatalytic CO₂ reduction reaction（CO₂RR）to produce formic acid is one effective route to achieve dual carbon goals and renewable energy storage.Developing efficient electrocatalysts is crucial to enhance the Faradaic efficiency of formic acid(FE_HCOOH)and retard the competing hydrogen evolution reaction.Bismuth（Bi）has high catalytic activity for the electroreduction of CO₂ to formic acid,which can inhibit competitive hydrogen evolution reactions and improve the performance of CO₂RR.Among them,Bi-based oxides are considered to be effective catalysts for improving CO₂RR selectivity.However,the relatively narrow potential range makes it difficult for Bi based electrocatalysts to be compatible with various energy converter devices,limiting their commercial applications.In response to this problem,Bi₂O₃ nanomaterials with different morphologies was designed and prepared.The results showed that the Bi₂O₃ nanoflower（Bi₂O₃NFs）exhibited a remarkable selectivity for formic acid of 95.2%at-1.1 V vs.RHE compared with Bi₂O₃ nanospheres（Bi₂O₃NPs）.Meanwhile,the FE_HCOOHremained above 80%in a wide potential range（-0.8 to-1.1 V vs.RHE）.Through studying the relationship of morphology and structure,it is speculated that the interaction of nanosheets in nanoflowers stabilizes the active site,ensures the activity of the catalyst and effectively inhibits the competitive hydrogen evolution reaction.At the same time,the high Bi-O structure content promotes the generation of the key intermediate*OCHO,and improves the production capacity of formic acid.After that,a series of Bi_aSn_bO_xwith different Bi/Sn molar ratios were prepared on the basis of Bi₂O₃NFs.The results showed that the addition of Sn improved the stability and selectivity of the catalyst,especially for Bi₂Sn₁O_xwith an appropriate Bi/Sn molar ratio,which achieved a significant FE_HCOOHof 98.6%at-1.1 V vs.RHE.Additionally,the catalyst exhibited outstanding durability during continuous operation for 24 h with FE_HCOOHmaintained at over 90%.The outstanding CO₂RR performance was attributed to the electronic delocalization effect between Bi and Sn tunes the overall electronic structure,resulting in the optimal binding energy at the bimetallic interface.Meanwhile,the optimal binding energy stabilizes active species,promoting the adsorption and activation of CO₂,accelerating the formation of the key intermediate*OCHO and improving the performance of CO₂RR.This work provides an interesting idea for the rational design of CO₂RR catalysts in the future.