Synthesis of Cu/CeO_2-x Nanocrystalline Heterodimers with Interfacial Active Sites To Promote CO₂ Electroreduction

Abstract

Synergistic effects at metal/metal oxide interfaces often give rise to highly active and selective catalytic motifs. So far, such interactions have been rarely explored to enhance the selectivity in the electrochemical CO 2 reduction reaction (CO 2 RR). Herein, Cu/CeO 2-x heterodimers (HDs) are synthesized and presented as one of the prime examples where such effects promote CO 2 RR. A colloidal seeded-growth synthesis is developed to connect the two highly mismatched domains (Cu and CeO 2-x) through an interface. The Cu/CeO 2-x HDs exhibit state-of-the-art selectivity towards CO 2 RR (up to ~80%) against the competitive hydrogen evolution reaction (HER) and high faradaic efficiency for methane (up to ~54%) at-1.2 V RHE , which is 5 times higher than that obtained when the Cu and CeO 2-x nanocrystals are physically mixed. Operando X-Ray absorption spectroscopy along with other ex-situ spectroscopies evidences the partial reduction from Ce 4+ to Ce 3+ in the HDs during CO 2 RR. A Density Functional Theory (DFT) study of the active site motif in reducing condition reveals synergistic effects in the electronic structure at the interface. The proposed lowest free energy pathway utilizes O-vacancy site with intermediates binding to both Cu and Ce atoms, a configuration which allows to break the CHO*/CO* scaling relation. The suppression of HER is attributed to the spontaneous formation of CO* at this interfacial motif and subsequent blockage of the Cu-sites.

Molecular tunability of surface-functionalized metal nanocrystals for selective electrochemical CO2 reduction

“…bimetallics and alloys) represents an additional degree of freedom that can contribute greatly to the CO 2 RR, as already demonstrated in many contributions. 34,[36][37][38][39][40][41][42][43] Finally, functionalized NCs can be integrated into more technologically relevant gas-diffusion electrodes in the future. 44 The electrocatalytic testing of the hybrid catalysts revealed that all of the ligands promote CO 2 RR over HER compared to the as-synthesized AgNCs, and interesting effects of the anchoring and tail groups on the tuning of the activity and selectivity have been discovered.…”

Ligand-mediated formation of Cu/metal oxide hybrid nanocrystals with tunable number of interfaces

“…In the past decade, colloidal chemistry has proven to be one of the most suitable synthetic methods to achieve tunability on hybrid materials at the nanoscale. [1][2][3][4][5][6][7][8][9][10] Indeed, colloidal hybrid nanocrystals (HNCs) have been utilized as the key components in a variety of applications spanning from catalysis to plasmonics to biomedicine and energy conversion. [1][2][3][4][5][6][7][8][9][10] Phase segregation, partial cation exchange, thermally induced coalescence and seeded growth are some of the strategies employed to access a huge library of HNCs.…”

“…[1][2][3][4][5][6][7][8][9][10] Indeed, colloidal hybrid nanocrystals (HNCs) have been utilized as the key components in a variety of applications spanning from catalysis to plasmonics to biomedicine and energy conversion. [1][2][3][4][5][6][7][8][9][10] Phase segregation, partial cation exchange, thermally induced coalescence and seeded growth are some of the strategies employed to access a huge library of HNCs. [1][2][3][4][5][6][7][8][9][10] Despite the beautiful examples reported in the literature, some material combinations remain more challenging or underexplored than others.…”

“…Non-noble metal/metal oxide HNCs are extremely interesting systems because of the unique synergistic interactions that arise at the interface between the two domains. 9,11,12 Nevertheless, synthetic strategies that enable precise control over the nal architecture of these NCs remain scarce. 9,[13][14][15] One of the challenges in these systems is the tendency of the non-noble metal domain to easily oxidize, which limits the reaction environment to organic solvent, and precludes the possibility of using the metal as a seed for the growth of the oxide domain, which is a common approach for HNCs.…”

“…9,11,12 Nevertheless, synthetic strategies that enable precise control over the nal architecture of these NCs remain scarce. 9,[13][14][15] One of the challenges in these systems is the tendency of the non-noble metal domain to easily oxidize, which limits the reaction environment to organic solvent, and precludes the possibility of using the metal as a seed for the growth of the oxide domain, which is a common approach for HNCs. 6,[16][17][18] In this work, we choose Cu/CeO 2 HNCs as one example of this class of materials because of the relevance of this interface for various applications, including thermal and electrochemical CO 2 conversion.…”