Selective CO₂ Reduction on 2D Mesoporous Bi Nanosheets

Abstract

The conversion of CO 2 to value-added products using electrical or solar energy represents an attractive means for the capture and utilization of atmospheric CO 2 . Formate is a popular product from CO 2 reduction, but its reaction selectivity is usually unsatisfactory. Tin-based materials have attracted most attention for formate production at present. Unfortunately, most of them only exhibit moderate selectivity in a narrow and highly cathodic potential window. In this study, we demonstrate that traditionally under-explored bismuth has a much greater potential for formate production than tin or other materials. Mesoporous bismuth nanosheets are prepared here by the cathodic transformation of atomic-thick bismuth oxycarbonate nanosheets. They enable the selective CO 2 reduction to formate with large current density, excellent Faradaic efficiency (~100%) over a broad potential window and great operation stability. Moreover, we integrate Bi nanosheets with an oxygen evolution reaction electrocatalyst in full cells, and achieve efficient and robust solar conversion of CO 2 /H 2 O to formate/O 2 .

Phosphomolybdic Acid‐Assisted Growth of Ultrathin Bismuth Nanosheets for Enhanced Electrocatalytic Reduction of CO2 to Formate

“…[19] AP Mo concentration of 5.0mm (pH % 1.75) was used instead of 2.0 mm to make sure that [PMo 12 O 40 ] 3À and its protonated forms are the dominant species, [33] similart ot hat in the presence of HNO 3 .T he SEM image (Figure S7 a) shows that nanoparticles of the size of about 100 nm as well as larger blocks were formed. [19] AP Mo concentration of 5.0mm (pH % 1.75) was used instead of 2.0 mm to make sure that [PMo 12 O 40 ] 3À and its protonated forms are the dominant species, [33] similart ot hat in the presence of HNO 3 .T he SEM image (Figure S7 a) shows that nanoparticles of the size of about 100 nm as well as larger blocks were formed.…”

“…Bismuth nitrate (Bi(NO 3 ) 3 ), phosphomolybdic acid (H 3 [PMo 12 O 40 ], PMo, 99.9 %,), nitric acid (HNO 3 ,7 0%), sodium bicarbonate (NaHCO 3 ), and sulfuric acid (H 2 SO 4 ,9 5-98 %) from Sigma-Aldrich, and CO 2 (Food grade, Aligal, Air Liquide) were used as supplied. Deionized water from aMilliQ-MilliRho purification system (resistivity 18 MW cm À1 )was used to prepare all aqueous solutions.…”

“…In this study,o xide-containing bismuth (Bi)n anosheets of about 4nmt hickness interconnected to form ap orous three-dimensional structure were synthe-sized by electrodeposition in the presence of phosphomolybdic acid under hydrogen evolution conditions. [12] 2D Bi nanosheets have also been generated by electroreduction of pre-synthesized nanosheet templates,s uch as BiOCl, [5i] BiOBr, [5e] BiOI, [5f] bismuth oxide sulfate and Bi 2 S 3 , [5h] bismuth subcarbonate (20-40nmt hick) synthesized by chemical reaction, [5j] andfew layer thin bismuth subcarbonateg enerated by electrochemical exfoliation. density in organic solvents with ionic liquids as the promoters.…”

Promises of Main Group Metal–Based Nanostructured Materials for Electrochemical CO2 Reduction to Formate

“…This is because the coupling to form C 2 –C 4 products requires the adsorption of multiple CO 2 molecules on surface and their concerted transformation, and is statistically challenged . Current state‐of‐the‐art electrocatalysts have the maximum selectivity of ≈100% for CO or formate, but only ≈60% for ethylene, ≈40% for acetate, and ≈15% for n ‐propanol . Poor selectivity not only results in ineffective utilization of electrolyzer electricity, but also incurs additional costs for the product separation.…”

A Disquisition on the Active Sites of Heterogeneous Catalysts for Electrochemical Reduction of CO2 to Value‐Added Chemicals and Fuel

“…While the activity of p‐block elements (i.e., Sn, Bi, In) for CO 2 RR are mostly attributed in literature to the presence of metastable oxidation states, defects and electronic tuning of catalyst surface, the role of exposed facets on CO 2 RR cannot be ruled out. For instance, Bi nanosheets catalyst that are generated from atomic‐thick Bi oxycarbonate nanosheets display a FE HCOO − of ≈100% at −0.9 V and this activity is partly attributed to the presence of Bi(101) and Bi(111) facets, which are demonstrated to lower free energy barrier for formation of *OCHO radical, facilitating CO 2 RR . Similar facet dependent DFT results with Sn, In and Bi catalysts were used as theoretical evidence to justify the catalytic activity of these catalysts for CO 2 RR .…”