In Situ-Activated Indium Nanoelectrocatalysts for Highly Active and Selective CO₂ Electroreduction around the Thermodynamic Potential

Abstract

Developing electrocatalysts for electrochemical CO2 reduction reaction (CO2RR) with pre-eminent activity and high selectivity at low overpotentials is very significant, but it still remains a formidable challenge. Herein, we report an in situ-activated indium nanoelectrocatalyst derived from InOOH nanosheets for active and selective CO2RR at ultralow overpotentials. Such a catalyst delivers near-unity CO2RR selectivity with formate as the main product, in a wide low-overpotential window of −0.25∼−0.49 V versus reversible hydrogen electrode (vs RHE). Significantly, the CO2RR activity reaches 151 mA cm–2 at −0.45 V vs RHE, comparable to the state-of-the-art Au-based catalysts. Impressively, full-cell CO2 electrolysis implements a record-high electricity-to-fuel energy-conversion efficiency of 76.0% and solar-to-fuel energy-conversion efficiency of 20.7%. Furthermore, in situ synchrotron X-ray diffraction reveals the dynamic formation of nanosized metallic indium, correlating well with CO2RR activity, also evidenced by cyclic voltammetry. Combined with theoretical calculations, it is confirmed that the in situ-generated metallic indium plays a dominant role in promoting formate formation by accelerating the second proton-coupled electron transfer process (*OCHO+ H+ + e – → *HCOOH). Consistent with experimental results, operando Raman spectra further demonstrate that in situ-activated indium nanocatalysts can facilitate formate production even at the thermodynamic potential. This work uncovers nanosized metallic indium as the highly active site and sheds light on the design of superior indium-based catalysts for CO2 electroreduction.

Identifying a Key Factor Determining Interfacial Electron Transfer in CO2 Reduction to Formate: Potential of Zero Charge

“…Particularly, the metallic Bi exhibits the highest partial current density of CO 2 -producing formic acid, e.g., −3.23 mA·cm –2 at −1.2 V vs RHE. Meanwhile, the HCOO – Faradaic efficiency (FE HCOO – ) for the four metals also decreases in the order of Bi, In, Sn, Pb at the same potential (Figure b), which is basically consistent with previous electrocatalytic studies. − Definitely, the metal Bi is still highly selective for the formation of HCOO – , and the maximum Faradaic efficiency (89.9%) is obtained at −1.2 V vs RHE, followed by In (68.9%), Sn (54.8%), and finally Pb (39.3%). Similarly, the maximum energy efficiency still decreases in the order of Bi, In, Sn, Pb (Figure c).…”

Triple-Phase Interface Engineering over an In2O3 Electrode to Boost Carbon Dioxide Electroreduction

“…10−14 High-performance electrocatalysts are thus needed to realize the CO 2 conversion with a high product yield and selectivity. 15−17 In recent years, In 2 O 3 has attracted special attention due to its nontoxicity, abundant reserve, and low cost, 18,19 and considerable efforts have been devoted to exploring effective strategies to establish efficient In 2 O 3 -based electrocatalytic systems for CO 2 RR. For example, size or shape regulation, 20 metal doping (V doping), 21 defect engineering (O-vacancies), 22 and heterojunction construction (In 2 O 3 -rGO, multi-walled carbon nanotube/In 2 O 3 , Cu/In 2 O 3 , In 2 O 3 /InN) 23−27 have been developed and confirmed to be able to elevate CO 2 RR performances of In 2 O 3 , which are mainly originated from the increase in electrochemically active surface areas, improvement of electrical conductivity, and optimization of intrinsic activity.…”

“…The unprecedented consumption of fossil fuels emits a large amount of CO 2 causing the deterioration of global climate. − Electrocatalytic reduction of CO 2 to fuels and value-added chemicals is regarded as one of the most important strategies to decrease the CO 2 concentration level in the atmosphere. − It is well known that the CO 2 reduction reaction (CO 2 RR) contains multi-step proton-coupled electron transfer processes, involving multiple intermediates and pathways, consequently resulting in sluggish reaction kinetics and complicated reduction products. − High-performance electrocatalysts are thus needed to realize the CO 2 conversion with a high product yield and selectivity. − In recent years, In 2 O 3 has attracted special attention due to its nontoxicity, abundant reserve, and low cost, , and considerable efforts have been devoted to exploring effective strategies to establish efficient In 2 O 3 -based electrocatalytic systems for CO 2 RR. For example, size or shape regulation, metal doping (V doping), defect engineering (O-vacancies), and heterojunction construction (In 2 O 3 -rGO, multi-walled carbon nanotube/In 2 O 3 , Cu/In 2 O 3 , In 2 O 3 /InN) − have been developed and confirmed to be able to elevate CO 2 RR performances of In 2 O 3 , which are mainly originated from the increase in electrochemically active surface areas, improvement of electrical conductivity, and optimization of intrinsic activity.…”

The role of oxygen-vacancy in bifunctional indium oxyhydroxide catalysts for electrochemical coupling of biomass valorization with CO2 conversion

“…It is worth noting that no obvious change is observed on the two In-O bands at 352 and 459 cm –1 with the varied potentials, that is, the oxidation state of In elements in InOOH-O V is well-maintained during CO 2 RR. This phenomenon is distinguished from other metal oxide catalysts (e.g., SnO 2 51 and InOOH 52 etc. ), which will be fully/partially reduced to metal with zero/lower valence, being the real active sites for CO 2 RR to formate.…”