Ultrastable Cu Catalyst for CO₂ Electroreduction to Multicarbon Liquid Fuels by Tuning C–C Coupling with CuTi Subsurface

Abstract

Production of multicarbon (C2+) liquid fuels is a challenging task for electrocatalytic CO2 reduction, mainly limited by the stabilization of reaction intermediates and their subsequent C−C couplings. In this work, we report a unique catalyst, the coordinatively unsaturated Cu sites on amorphous CuTi alloy (a‐CuTi@Cu) toward electrocatalytic CO2 reduction to multicarbon (C2‐4) liquid fuels. Remarkably, the electrocatalyst yields ethanol, acetone, and n‐butanol as major products with a total C2‐4 faradaic efficiency of about 49 % at −0.8 V vs. reversible hydrogen electrode (RHE), which can be maintained for at least 3 months. Theoretical simulations and in situ characterization reveals that subsurface Ti atoms can increase the electron density of surface Cu sites and enhance the adsorption of *CO intermediate, which in turn reduces the energy barriers required for *CO dimerization and trimerization.

Boosting CO2 electroreduction towards C2+ products via CO* intermediate manipulation on copper-based catalysts

“…This method by constructing a metal–substrate interface to increase the oxidation state of Cu provides an avenue to promote C–C coupling. Extensive experimental results have shown that Cu + on non-copper substrates such as metal oxides, 118,119 nitrides 120 and even metals 121 can also promote the formation of C 2+ products. For example, Lee et al synthesized Cu/ceria catalysts (sub-10 nm) with a high density of interfaces and interconnected structure of CuO and CeO 2 nanocrystals by impregnating a copper precursor into ceria/C and subsequent calcination in air (Fig.…”

Phosphorus‐Doped Graphene Aerogel as Self‐Supported Electrocatalyst for CO2‐to‐Ethanol Conversion

“…[ 1,37 ] The signals located at 850 cm −1 represented the C─C─O symmetric stretching, indicating the successful C─C coupling and EtOH formation. [ 2 ] Furthermore, time‐dependent in situ Raman exhibited the decreased intensity of *CO and v CO 3 2− signal during 0–360 s in the first round, whereas the signal for C─C─O gradually increased (Figure 3b). After removing the voltage for 180 s, the signals from carbonate, *CO, and C─C─O stretching disappeared.…”

“…The free energy diagrams illustrated that the shared ratedetermining step (RDS) was the final protonation step (Figure 4c), in which EtOH is desorbed with an energy barrier of 0.86 eV for path I and path II and 0.96 eV for path III. Since path I and path II showed the same energy barrier for the RDS, the C─C coupling step was further considered as the second RDS, whose energy barrier was 0.68 eV for path II and 0.66 eV for path I (Figure S32 [2,37] The energy barriers for C 2 H 4 generation were further calculated to get insight into the suppressed C 2 H 4 production. As shown in Figure S35 (Supporting Information), *CH 2 CHO spontaneous transformed to *CH 2 CHOH for EtOH generation, while the energy barrier for *CH 2 CHOH→ *CH 2 CH (1.37 eV) is much higher than that of *CH 2 CHOH→ *CH 2 CH 2 OH (0.45 eV).…”

“…[10,18] Nevertheless, nitrogen-doping (N-doping) has been proven to be a feasible strategy for boosting CO 2 RR, but the products are mainly limited to CO. [17,19,20] During the conversion of CO 2 to EtOH, various intermediates and transition states are involved, which will significantly alter the activity and selectivity. [2,11] The adsorption of *CO intermediate has been widely acknowledged for the C─C coupling. [1,21] Whereas, the facile desorption of *CO on conventional carbon electrocatalysts results in difficulties for the formation of C 2+ products.…”

“…The conversion of carbon dioxide (CO 2 ) via renewable but intermittent electricity (e.g., from solar and wind) is regarded as a promising approach to close the anthropogenic carbon cycle and provide value‐added chemical feedstocks. [ 1–3 ] Electrochemical CO 2 reduction reaction (CO 2 RR) has been intensively investigated (Table S1, Supporting Information), and mostly, tends to selectively form 2‐electron‐transfer products, i.e., carbon monoxide (CO) and formic acid (HCOOH). [ 4,5 ] Multicarbon (C 2+ ) products, particularly ethanol (C 2 H 5 OH, EtOH), are more appreciated due to the higher energy density (26.8 MJ kg −1 ) and ease of storage as liquid fuels.…”