Ultrathin bismuth nanosheets from in situ topotactic transformation for selective electrocatalytic CO2 reduction to formate

Abstract

Electrocatalytic carbon dioxide reduction to formate is desirable but challenging. Current attention is mostly focused on tin-based materials, which, unfortunately, often suffer from limited Faradaic efficiency. The potential of bismuth in carbon dioxide reduction has been suggested but remained understudied. Here, we report that ultrathin bismuth nanosheets are prepared from the in situ topotactic transformation of bismuth oxyiodide nanosheets. They process single crystallinity and enlarged surface areas. Such an advantageous nanostructure affords the material with excellent electrocatalytic performance for carbon dioxide reduction to formate. High selectivity (~100%) and large current density are measured over a broad potential, as well as excellent durability for >10 h. Its selectivity for formate is also understood by density functional theory calculations. In addition, bismuth nanosheets were coupled with an iridium-based oxygen evolution electrocatalyst to achieve efficient full-cell electrolysis. When powered by two AA-size alkaline batteries, the full cell exhibits impressive Faradaic efficiency and electricity-to-formate conversion efficiency.

Size Controllable Metal Nanoparticles Anchored on Nitrogen Doped Carbon for Electrocatalytic Energy Conversion

“…The onset potentials for CO 2 RR and OER are approximately À 1.8 V and 1.0 V vs. Fc/Fc + , respectively. This value is considerably lower than the value of~6 mA cm À 2 reported by Han et al [20] in an aqueous bicarbonate medium with Bi nanosheet modified carbon paper as the cathode and Ir/C modified carbon paper as the anode. A two-compartment electrochemical cell was employed to conduct the artificial photosynthesis experiment (Figure 6b) with CoNC-400 modified carbon cloth (1 cm × 3 cm) as the cathode and anode.…”

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

“…Due to difficulties associated with the direct synthesis and engineering of metallic Bi nanostructures, it is more viable to start with precatalysts composed of oxides, oxyhalides, carbonates, or sulfides, and then cathodically convert them to metallic Bi for CO 2 RR. Following this guiding principle, our group reported the preparation of ultrathin Bi nanosheets from the in situ topotactic transformation of BiOI nanosheets ( Figure 8 a–c) . Interestingly, we found that the 2D geometry and single crystallinity were well‐preserved after the cathodic conversion due to the intrinsic structural correlation between BiOI and metallic Bi.…”

“…Liquid products (such as formate, methanol, ethanol, acetate, and so on) accumulated in the catholyte at the end of tests can be measured using proton nuclear magnetic resonance ( 1 H NMR). Alternatively, we find that ion chromatography is an effective tool for quantifying the amount of formate in the catholyte . It has a lower detention limit (≈100 ppb) than NMR (1–10 ppm), and is easier to operate.…”

“…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

“…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 . In addition, SnO 2 (110) is reported to play a positive role in dictating formate generation during CO 2 RR with a number of literatures with SnO 2 nanoparticle catalysts ascribing the importance of this facet …”