Oxygen Functionalized Copper Nanoparticles for Solar-Driven Conversion of Carbon Dioxide to Methane

Abstract

Solar conversion of carbon dioxide (CO2) into hydrocarbon fuels offers a promising approach to fulfill the world’s ever-increasing energy demands in a sustainable way. However, a highly active catalyst that can also tune the selectivity toward desired products must be developed for an effective process. Here, we present oxygen functionalized copper (OFn-Cu) nanoparticles as a highly active and methane (CH4) selective catalyst for the electrocatalytic CO2 reduction reaction. Our electrochemical results indicate that OFn-Cu (5 nm) nanoparticles with an oxidized layer at the surface reach a maximum CH4 formation current density and turnover frequency of 36.24 mA/cm2 and of 0.17 s–1 at the potential of −1.05 V vs RHE, respectively, exceeding the performance of existing Cu and Cu-based catalysts. Characterization results indicate that the surface of the OFn-Cu nanoparticles consists of an oxygen functionalized layer in the form of Cu2+ (CuO) separated from the underneath elemental Cu by a Cu+ (Cu2O) sublayer. Density functional theory calculations also confirm that presence of the O site at the CuO (101) surface is the main reason for the enhanced activity and selectivity. Using this catalyst, we have demonstrated a flow cell with an active area of 25 cm2 that utilizes solar energy to produce 7.24 L of CH4 after 10 h of continuous process at a cell power density of 30 mW/cm2.

Kinetically Stable Oxide Overlayers on Mo3P Nanoparticles Enabling Lithium–Air Batteries with Low Overpotentials and Long Cycle Life

“…The Mo 3 P nanoparticles were synthesized using a facile colloidal chemistry method followed by a thermal sintering process (Section S1, Supporting Information). [ 21,39 ] X‐ray diffraction (XRD) patterns of the studied catalyst are shown in Figure S1, Supporting Information confirming the crystalline structure of the synthesized catalysts (Section S2, Supporting Information) with an average crystallite size of 25 nm using the Scherrer equation (Section S2, Supporting Information). The preparation and characterization of other studied catalysts, such as, MoS 2 nanoflakes, Pt, and Au nanoparticles are explained in Sections S1 and S2, Supporting Information.…”

“…Our measurements (Figure S29, Supporting Information) indicate 0.25 eV lower work function for the oxidized Mo 3 P (3.18 eV) compared with pristine Mo 3 P (3.43 eV) further supporting the existence of the oxide overlayer on Mo 3 P that can be a reason for high activity of this catalyst for both ORR and OER. [ 39,68–73 ]…”

Gold-Like Activity, Copper-Like Selectivity of Heteroatomic Transition Metal Carbides (M2C) for Electrocatalytic Carbon Dioxide Reduction Reaction

“…As shown in Fig. 1b, S2) 46,[48][49][50][51][52][53][54] . Supplementary Table S2b indicates that the j CH4 of W 2 C NFs is 3.6 and 4.2 times higher than recently studied La 2 CuO 4 (-117 mA/cm 2 at -1.4 V vs RHE) 51 and Cu-N (-100 mA/cm 2 at -1.0 V vs RHE) 48 , respectively.…”

“…The TMC NFs i.e., W 2 C, Mo 2 C, Nb 2 C and V 2 C were synthesized using a carburization process followed by the liquid exfoliation technique (Supplementary section S1) 27,44,45 . The electrocatalytic performance of TMC NFs with the similar crystallite sizes (25.4±5 nm) were then studied in a three-electrode cell and compared with Au and Cu nanoparticles (NPs), conventional catalysts for this reaction, 46 under identical experimental conditions (Supplementary section S2). To improve the CO 2 RR performance in competing with hydrogen evolution reaction (HER), we have employed a mixture of 3 M potassium hydroxide (KOH) and 2 M choline-chloride (CC) solution (KOH:CC (3M:2M)) as the electrolyte in this study 47 .…”

“…The stability of the choline chloride electrolytes was studied by conducting nuclear magnetic resonance (NMR) and 13 CO 2 isotope experiments (Supplementary section S14 and S15) 27,46,71 . The 1 H and 13 C NMR spectra reveal similar peak areas and chemical shifts for fresh and used electrolytes indicating no generation of new diamagnetic species or change in the choline chloride structure under applied potential of -1.05 V vs RHE (Supplementary Figs.…”