二氧化碳转化已成为现今世界研究的热点. 本工作采用原位电化学转化的策略, 将简单溶剂热法合成的层状甲酸氧铋纳米花(BiOCOOH NFs)还原为带有大量晶格位错的多孔铋纳米花(p-Bi NFs). 研究结果表明, p-Bi NFs电催化二氧化碳转化为甲酸盐具有较小的过电位(436 mV). 在–1.8 V(相对饱和甘汞电极, vs. SCE)时, 甲酸盐的分电流密度(j_formate)高达24.4 mA•cm^-2, 法拉第效率(FE_formate)为96.7%, 且在超过500 mV的宽电位窗口内FE_formate超过90%, 并具有很好的稳定性. 该催化剂的高催化性能可归因于前驱体晶格坍塌和重构而形成特殊的多孔粗糙的微纳多级结构, 其表面富含晶格位错和缺陷等高本征活性位, 且具有较强的电子传递能力. 本研究为设计合成高性能的电催化二氧化碳还原产甲酸催化剂提供了新的思路.

The conversion of carbon dioxide has become a hot topic in the world today. Here, we adopt the strategy of in-situ electrochemical transformation to reduce layered bismuth oxide formate nanoflowers (BiOCOOH NFs) self-assembled with nanosheets synthesized by simple solvothermal method to porous bismuth nanoflowers (p-Bi NFs) with a large number of lattice dislocations. Specifically, 1.0 g Bi(NO₃)₃•5H₂O was ultrasonically dissolved in 10 mL N,N-dimethylformamide (DMF), then 70 mL deionized water was added to the above solution, and the resulting solution was ultrasonicated for 10 min at room temperature to ensure that all reagents were uniformly dispersed. The resulting solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave, kept at 120 ℃ for 20 h, and then naturally cooled to room temperature. The results show that the minimum overpotential of the electrochemical reduction of carbon dioxide to formate is 436 mV. When the catalyst loading is 0.5 mg/cm², the partial current density of formate (j_formate) is as high as 24.4 mA•cm^-2, which is 5.5 times that of commercial bismuth (Commercial Bi); and the Faraday efficiency (FE_formate) of formate is 96.7% at –1.8 V versus saturated calomel electrode (vs. SCE). The FE_formate is over 90% in a wide potential window of over 500 mV. Moreover, the p-Bi NFs electrocatalyst is stable in formate production for more than 10 h in CO₂-saturated 0.5 mol•L^-1 KHCO₃ electrolyte. Compared with the normalized electrochemical surface area (ECSA), it was found that the j_formate of p-Bi NFs was still about 4.5 times higher than that of Commercial Bi. The high catalytic performance of the catalyst can be attributed to the unique micro/nano hybrid structure derived from the lattice collapse and reconstruction of precursors, resulting in porous and rough surface and containing high density of active sites with lattice dislocations and defects. This study provides new insights into designing and synthesizing electrocatalysts with high performance for carbon dioxide reduction to formate.