(406e) Tuning the Electronic Structure of Mxene As a Support for Electrochemical CO2 Reduction Catalysts

The electrochemical CO₂ reduction reaction (CO₂RR) is a promising route to valorize CO₂ and realize net-zero emissions. To optimize this reaction, it is crucial to tune both the microenvironment and the electrocatalyst support. To this end, MXene has shown promise in the literature as a promising class of materials with tunable composition and electronic structure as an electrocatalyst support. Our fundamental investigation examines the support effect of titanium carbide-based MXene (Ti₃C₂T_x) on Ag-catalyzed CO₂RR.

Herein, we report that the electronic structure of Ti₃C₂T_x can be tuned by introducing cations, with particular emphasis on the in-situ formation of Ag nanoparticles (NPs) via Ag⁺ loading (with Ti₃C₂T_x as a de facto reducing agent). Controlling the electronic structure of Ti₃C₂T_x is critical for balancing the competition between CO₂RR and HER, thereby tuning overall selectivity and activity. Our systematic investigations reveal that cations with lower reduction potentials (eg. Na⁺, Co²⁺, Ni²⁺) do not significantly alter CO₂RR performance, whereas cations with higher reduction potentials (eg. Cu²⁺, Ag⁺) can modify Ti₃C₂T_x’s electronic structure. Specifically, in-situ reduced Ag NPs on Ti₃C₂T_x yield a higher Ti oxidation state and increased Ti–O bond content compared to samples containing physically mixed Ag NPs loaded onto MXene. This electronic restructuring suppresses competing HER and enhances the CO Faradaic efficiency (FE). For example, the CO FE rises from 8.1 % (partial current density -2.0 mA cm^-2) to 49.6 % (partial current density -20.1 mA cm^-2) at -1.4V vs. RHE. Additionally, the ratio of CO to H₂ in the syngas product can be controllably adjusted from 1:3 to 1:1.

This work contributes to the fundamental understanding of MXene-based catalysts and provides a strategic pathway to systematically tune the CO₂RR/HER balance for efficient carbon utilization. Finally, this presentation will give insights into the outlook for MXene as a tunable electrocatalyst support.