Alloying as a Strategy to Boost the Stability of Copper Nanocatalysts during the Electrochemical CO₂ Reduction Reaction

Abstract

Copper nanocatalysts are among the most promising candidates to drive the electrochemical CO2 reduction reaction (CO2RR). However, the stability of such catalysts during operation is sub-optimal, and improving this aspect of catalyst behavior remains a challenge. Here, we synthesize well-defined and tunable CuGa nanoparticles (NPs) and demonstrate that alloying Cu with Ga considerably improves the stability of the nanocatalysts. In particular, we discover that CuGa NPs containing 17 at. % Ga preserve most of their CO2RR activity for at least 20 h while Cu NPs of the same size reconstruct and lose their CO2RR activity within 2 h. Various characterization techniques, including X-ray photoelectron spectroscopy and operando X-ray absorption spectroscopy, suggest that the addition of Ga suppresses Cu oxidation at open-circuit potential (ocp) and induces significant electronic interactions between Ga and Cu. Thus, we explain the observed stabilization of the Cu by Ga as a result of the higher oxophilicity and lower electronegativity of Ga, which reduce the propensity of Cu to oxidize at ocp and enhance the bond strength in the alloyed nanocatalysts. In addition to addressing one of the major challenges in CO2RR, this study proposes a strategy to generate NPs that are stable under a reducing reaction environment.

Stability Issues in Electrochemical CO2Reduction: Recent Advances in Fundamental Understanding and Design Strategies

“…[111] Recently, Okatenko et al presented a systematic investigation to reveal the alloying effect on structure evolution and stability of Cu nanocatalysts during CO 2 RR. [106] The CuGa 17 nanoparticles (NPs) were synthesized from a seeded-growth method to first deposit Ga layer on surface of pristine Cu NPs, followed by thermal amalgamation to construct CuGa 17 alloy nanocatalyst. Electrochemical measurements indicate the higher stability of CuGa 17 for methane production in comparison to that of Cu NPs (Figure 7e,f).…”

“…g) Stability mechanism on Cu NPs and CuGa 17 NPs. Reproduced with permission [106]. Copyright 2023, American Chemical Society.…”

High-Power CO2-to-C2 Electroreduction on Ga-Spaced, Square-like Cu Sites

“…Herein, we rationally developed an atomically ordered Cu 9 Ga 4 intermetallic compound as an efficient electrocatalyst for CO 2 -to-C 2 conversion. The Cu 9 Ga 4 intermetallic compound contains Cu(100)-like square structural units as more efficient sites than Cu(100) and Cu(111) for *CO binding and coupling, and the gallium (Ga) atoms function as inert nodes that weakly bind *CO or *H species, − thus allowing to reduce *CO repulsion. The Cu 9 Ga 4 catalyst exhibited one of the highest electrochemical CO 2 -to-C 2 conversion performances, including the partial current density of C 2 production (| j C2 |) as 1207 mA cm –2 and the corresponding Faradaic efficiency (FE C2 ) of 71%.…”

Density functional theory calculation of two-dimensional transition metal–hexaiminotriphenylene (TM-HITP) electrocatalytic CO2 reduction

“…37,38 Subsequently, extensive research has been carried out on Cu catalysts in the field of catalytic science and technology. Amongst these efforts, Raffaella Buonsanti's [39][40][41][42][43] work has used alloying techniques to improve the stability of Cu nanocatalysts during electrochemical CO 2 reduction reactions. In addition, co-catalytic studies have been carried out to increase ethylene production from CO 2 reduction.…”