Au Nanocrystals@Defective Amorphous MnO₂ Nanosheets Core/Shell Nanostructure with Effective CO₂ Adsorption and Activation toward CO₂ Electroreduction to CO

Abstract

MnO 2 -60 NSs displayed partial current densities of 3.6 mA cm −2 at −0.7 V and 14.3 mA cm −2 at −1.0 V for CO. It also exhibited outstanding stability with negligibly decreased current densities after 12 h electrocatalysis at −0.5, −0.7, and −0.9 V. The synergy between Au NCs core and a-MnO 2 NSs shell is contributed to its prominent activity, selectivity, and stability for CO 2 ER to CO. This work integrates conductivity promotion and defect engineering by noble-metal@defective amorphous oxide core/shell nanostructure toward improved CO 2 ER.

Br-Doped CuO Multilamellar Mesoporous Nanosheets with Oxygen Vacancies and Cetyltrimethyl Ammonium Cations Adsorption for Optimizing Intermediate Species and Their Adsorption Behaviors toward CO2 Electroreduction to Ethanol with a High Faradaic Efficiency

“…To gain deep insight into the catalytic mechanism, the electrochemically active surface area (ECSA) of each product was evaluated via C dl through CV measurements at different scan rates (Figure S14). As shown in Figure a, the C dl value of Br 1.95% -CuO was 4.65 mF cm –2 , far exceeding that of CuO (0.62 mF cm –2 ), indicating Br 1.95% -CuO can provide more active sites for CO 2 ER, which brought more open coordination sites for intermediates binding at greatly increased contacted interface with the electrolyte . However, its C dl value was slightly smaller than that of Br 1.84% -CuO (5.21 mF cm –2 ), due to adsorbed CTA + cations partially covering the active sites on the catalyst’s surface .…”

“…Following the detailed experimental analysis of the reaction intermediates, a reaction pathway for CO 2 ER to ethanol on Br-doped CuO multilamellar mesoporous nanosheets with oxygen vacancies and CTA + cations adsorption was proposed. First, oxygen vacancies with positive charges can accumulate rich electrons from the electrode and form electron-rich regions on their surfaces, which were favorable to adsorbing CO 2 molecules, like electron-rich Br sites, where the electrons flowed from localized electrons around oxygen vacancies or Br sites to the vacant orbitals of CO 2 molecules. , The oxygen vacancies lowered the activation energy barrier of the CO 2 molecule, ,, while the formation of the Br–C bond weakened the C–O bond of the CO 2 molecule, which both promoted linear CO 2 molecules converted into bent *CO 2 – species adsorbed on oxygen vacancies and Br sites. The O vacancies modulated Cu sites with different charge distribution, in which the Cu sites near the O vacancies showed negative charge enriched state. , *CO 2 – species were then reduced to *CO species via proton coupled-electron transfer (PCET) step, forming positively charged linear *CO L absorbed on Cu sites near O vacancies and Br sites and negatively charged bridge *CO B adsorbed on Cu sites not near O vacancies.…”

“…As shown in Figure 6a, the C dl value of Br 1.95% -CuO was 4.65 mF cm −2 , far exceeding that of CuO (0.62 mF cm −2 ), indicating Br 1.95% -CuO can provide more active sites for CO 2 ER, which brought more open coordination sites for intermediates binding at greatly increased contacted interface with the electrolyte. 43 However, its C dl value was slightly smaller than that of Br 1.84% -CuO (5.21 mF cm −2 ), due to adsorbed CTA + cations partially covering the active sites on the catalyst's surface. 42 To explore the intrinsic property of CO 2 ER, the partial current densities of C 2 H 5 OH on Br 1.95% -CuO and Br 1.84% -CuO were normalized via ECSAs.…”

Efficacious CO2 Adsorption and Activation on Ag Nanoparticles/CuO Mesoporous Nanosheets Heterostructure for CO2 Electroreduction to CO

“…The electrons were transferred from Ag to Cu in Ag NPs/CuO MNSs, enabling CO 2 molecules to adsorb on Cu sites at the interfacial boundaries of CuO . In addition, the positively charged oxygen vacancies on the surfaces of CuO MNSs can produce electron-rich zones by accumulating electrons from the electrode, facilitating CO 2 molecule adsorption, and reducing their activation energy barrier. ,− Ag NPs in the Ag NPs/CuO MNSs heterostructure endowed the sample with good electrical conductivity and boosted the adsorbed CO 2 molecules to obtain electrons from the catalyst; consequently, linear CO 2 molecules were activated to winding *CO 2 – intermediates. Thereafter, *CO 2 – intermediates obtained protons from HCO 3 – and protonated to *COOH intermediates, wherein the carbonyl groups in *COOH show O-terminal adsorption on Cu sites and C-terminal adsorption on Ag sites because the Ag–CuO interface can decrease the energy barrier of *COOH generation, which augmented the bonding stability and strength of *COOH .…”

Manipulation on Two-Dimensional Amorphous Nanomaterials for Enhanced Electrochemical Energy Storage and Conversion

“…In a work by Lu et al, a unique hybrid catalyst of Pd hydride nanocubes encapsulated within amorphous Ni-B nanosheets (PdH x @Ni-B) was synthesized and demonstrated an impressive ORR activity (1.05 mg Pd −1 at 0.90 V versus reversible hydrogen electrode) and stability (10,000 potential cycles) (Figure 7b) [93]. Gao et al constructed a composite catalyst of Au nanocrystals@amorphous MnO 2 nanosheets with CO faradic efficiency (FE) of 90.5% for CRR at −0.7 V versus reversible hydrogen electrode [94]. The core/shell nanostructure brings about the interaction between Au and amorphous MnO 2 nanosheets, which contributed to its performance (Figure 7c).…”