In Situ Generation of Pseudorutile Oxide as the Cathode for Direct Electrolysis of CO2

Xiaojing Liu; Jiupai Ni; Chengsheng Ni

doi:10.1021/acs.inorgchem.3c02191

In Situ Generation of Pseudorutile Oxide as the Cathode for Direct Electrolysis of CO₂

Inorg Chem. 2023 Sep 11;62(36):14748-14756. doi: 10.1021/acs.inorgchem.3c02191. Epub 2023 Aug 30.

Authors

Xiaojing Liu^{1

2}, Jiupai Ni^{1

2}, Chengsheng Ni^{1

2}

Affiliations

¹ College of Resources and Environment, Southwest University, Beibei, Chongqing 400715, China.
² National Base of International S&T Collaboration on Water Environmental Monitoring and Simulation in Three Gorges Reservoir Region, Chongqing 400716, China.

PMID: 37647591
DOI: 10.1021/acs.inorgchem.3c02191

Abstract

The conversion of CO₂ into CO in high-temperature solid oxide electrolysis cells (SOECs) is an attractive route for the CO₂ utilization using the intermittent renewables. The low-cost and highly catalytic cathode is important for the direct electrolysis of pure CO₂. In this study, non-perovskite Fe_0.5Mg_0.25+0.5xTi_0.25-0.5xNb_1-xMo_xO₄ oxides (denoted as Mo-x when x is equal to 0, 0.1, and 0.2) are evaluated as the cathode of an SOEC for the direct electrolysis of CO₂. Mo⁶⁺ doping converted the wolframite Mo-0 into an α-PbO₂-type with cation disordering, while further doping to Mo-0.2 showed a wolframite with cation ordering again. The SOEC with Mo-0.2 as the cathode exhibits the best electrochemical performance for the direct electrolysis of CO₂ as a large portion of the oxide converted into oxygen-deficient pseudorutile-type oxide with a nominal formula of M₅O₉ (M = cation). The pseudorutile, a crystallographic shear phase of rutile, can be obtained after 60 h of direct electrolysis in CO₂ at a 1.3 V bias rather than a reduction under 5% H₂. The SOEC with Mo-0.2 as the cathode imparted a stable current density of 0.45 A cm^-2, which could be related to the production of pseudorutile decorated with nanoparticles of MoO₂. These results show that molybdenum doping is an effective strategy for developing oxygen-deficient rutile (pseudorutile) for the electrolysis of CO₂.