Carbon dioxide electroreduction on single-atom nickel decorated carbon membranes with industry compatible current densities

Abstract

Carbon dioxide electroreduction provides a useful source of carbon monoxide, but comparatively few catalysts could be sustained at current densities of industry level. Herein, we construct a high-yield, flexible and self-supported single-atom nickel-decorated porous carbon membrane catalyst. This membrane possesses interconnected nanofibers and hierarchical pores, affording abundant effective nickel single atoms that participate in carbon dioxide reduction. Moreover, the excellent mechanical strength and well-distributed nickel atoms of this membrane combines gas-diffusion and catalyst layers into one architecture. This integrated membrane could be directly used as a gas diffusion electrode to establish an extremely stable three-phase interface for high-performance carbon dioxide electroreduction, producing carbon monoxide with a 308.4 mA cm^-2 partial current density and 88% Faradaic efficiency for up to 120 h. We hope this work will provide guidance for the design and application of carbon dioxide electro-catalysts at the potential industrial scale.

Fig. 1. Physical characterizations of NiSA/PCFM.

a Synthesis strategy of NiSA/PCFM. b Digital images and c stress-strain curve of NiSA/PCFM membrane.

Fig. 2. Morphological and structural characterizations of NiSA/PCFM.

a The water contact angles of NiSA/PCFM spraying with a little amount of Nafion solution. b Cross-sectional and c high-resolution SEM images of NiSA/PCFM. d HR-TEM image of NiSA/PCFM, the inset of (d) displays the lattice fringe. e EDS mapping of an independent NiSA/PCFM nanofiber. f Magnified HAADF-STEM images of NiSA/PCFM, those white dots are supposed to be Ni single atoms. Scale bars, 100 μm (b), 1 μm (c), 0.5 μm (d), and 2 nm (f).

Fig. 3. Chemical analysis of NiSA/PCFM.

a N₂ sorption isotherms of NiSA/PCFM, inset shows the pore size distribution. b CO₂ adsorption amount of various catalysts. c N 1s XPS spectra of NiSA/PCFM. d XANES spectra at the Ni K-edge of Ni foil, NiO and NiSA/PCFM; e The Fourier transform of EXAFS data for three samples; f Fitting for the EXAFS data of NiSA/PCFM, inset is the Ni-N₄-C structure, Ni (green sphere), N (blue sphere), and C (gray sphere).

Fig. 4. Electrocatalytic CO₂ reduction.

a CO faradaic efficiency and b partial current densities for three catalysts at various cathode potentials in H-type cell. c CO faradaic efficiencies, d partial current densities of NiSA/PCFM at various cathode potentials in different cells. e Long-term stability tests in GDE cell and f H-type cell at –1.0 V_RHE, respectively.

Fig. 5. Proposed mechanism of NiSA/PCFM.

a Free energy diagram of CO₂ to adsorbed *COOH intermediate on N-C and Ni-N₄-C doped graphene structure; b Comparisons of Tafel plots. c Graphic illustration of a GDE device; Schematic for d NiSA/PCFM membrane directly used as GDE and e typical GDE cell with catalyst powder loaded onto a gas-diffusion layer via polymer binder.