Interfacial Electronic Interaction in In₂O₃/Poly(3,4-ethylenedioxythiophene)-Modified Carbon Heterostructures for Enhanced Electroreduction of CO₂ to Formate

Abstract

Formate, as an important chemical raw material, is considered to be one of the most promising products for industrialization among CO2 electroreduction reaction (CO2RR) products, but it still suffers from poor selectivity and a low formation rate at a high current density on account of the competitory hydrogen evolution reaction. Herein, the heterogeneous nanostructure was constructed by anchoring In2O3 nanoparticles on poly­(3,4-ethylenedioxythiophene) (PEDOT)-modified carbon black (In2O3/PC), in which the PEDOT polymer interface layer could immobilize In2O3 nanoparticles and obtain a notable reduction in electron transfer resistance among the In2O3 particles, showing a 27% increase in the total electron transfer rate. The optimized In2O3/PC with rich heterogeneous interfaces selectively reduced CO2 to formate with a high FE of 95.4% and a current density of 251.4 mA cm–2 under −1.18 V vs RHE. Also, the formate production rate for In2O3/PC was up to 7025.1 μmol h–1 cm–2, surpassing most previously reported CO2RR catalysts. The in situ XRD results revealed that In2O3 particles were reduced to metallic indium (In) as catalytic active sites during CO2RR. DFT calculations verified that a strong interface interaction between In sites and PC induced electron transfer from In sites to PC, which could optimize the charge distribution of active sites, accelerate electron transfer, and elevate the p-band center of In sites toward the Fermi level, thereby lowering the adsorption energy of *OCHO intermediates for CO2 conversion to formate.

Heterojunction catalysts for CO2–HCOOX interconversion cycles

“…In 2 O 3 /PC presents an outstanding electrocatalytic selectivity for formate with an FE of 95.4%, an extremely high formate current density of 239.8 mA cm −2 at −1.18 V vs. RHE, and a high stability for 75 h continuous electrolysis test. 121 There are strong interface electronic interactions between In metal and PC in the In/PC heterojunction confirmed by both experiments and DFT results, elevating the p-band center of In metal active sites to the Fermi level, resulting in the lower formation energies of the *OCHO, which is the key intermediate for converting CO 2 to the target production formate.…”

“…Among all the catalysts investigated to date, In-based electrocatalysts with excellent selectivity toward targeted formate and non-toxicity have attracted much attention. 121 Sn and Bi metals, as the low-cost, low-toxic, and earth-abundant metal elements, show high selectivity to formic acid and a high activity during the electrocatalytic CO 2 reduction reaction. 120,122 Therefore, Sn-, Bi-, and In-based catalysts are promising candidates for large-scale real-world use, because of their merits of low price, abundance, and environmental benignancy, compared to the noble metals Au, Pd, and Ag, as well as the toxic metals Pb, Hg, and Cd.…”

“…In addition to metals, for oxides and nitrides of these metals the construction of heterojunctions is also an effective method for improving the activity, selectivity, and stability of catalysts for the ECO 2 RR reaction. 116,121,125 The construction of semiconductor–semiconductor heterojunctions will also form electron transfer at the interface to achieve changes in the electronic structure of the active sites, thereby promoting the adsorption of substrates and key intermediates, further improving catalytic activity and selectivity.…”

Regulation Strategy of Nanostructured Engineering on Indium‐Based Materials for Electrocatalytic Conversion of CO2

“…In addition, the adsorption-free energy of intermediates and the selectivity of specific products can also be promoted by forming heterostructure for CO 2 RR. In recent years, there have been many achievements in this area, such as the design of InO x @CuO, [222] CuO-In 2 O 3 , [223] Cu/In, [206] In 2 O 3 -ZnO, [224] In-O-ultrathin-SnS 2 , [225] In 2 O 3 /PC, [226] In/In 2 O 3−x , [227] In 2 O 3 -CeO x [228] with heterostructures. Those materials have been demonstrated that the constructed heterostructures can greatly enhance the performance of In-based catalysts for CO 2 RR.…”

“…Heterostructures are extremely helpful to enhance the selectivity of the most common formic acid products in In-based catalysts, such as the constructed In 2 O 3 /PC, [226] In/In 2 O 3−x [227] and other heterojunction materials. The recently proposed a special crystalline-amorphous heterostructure, which shows unique potential in CO 2 RR.…”