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. 2023 Aug 25;13(17):2421.
doi: 10.3390/nano13172421.

MOF Template-Derived Carbon Shell-Embedded CoP Hierarchical Nanosheet as Bifunctional Catalyst for Overall Water Splitting

Affiliations

MOF Template-Derived Carbon Shell-Embedded CoP Hierarchical Nanosheet as Bifunctional Catalyst for Overall Water Splitting

Mei-Jun Liu et al. Nanomaterials (Basel). .

Abstract

The design of earth-abundant and highly efficient bifunctional electrocatalysts for hydrogen evolution and oxygen evolution reactions (HER/OER) is crucial for hydrogen production through overall water splitting. Herein, we report a novel nanostructure consisting of vertically oriented CoP hierarchical nanosheet arrays with in situ-assembled carbon skeletons on a Ti foil electrode. The novel Zeolitic Imidazolate Framework-67 (ZIF-67) template-derived hierarchical nanosheet architecture effectively improved electrical conductivity, facilitated electrolyte transport, and increased the exposure of the active sites. The obtained bifunctional hybrid exhibited a low overpotential of 72 mV at 10 mA cm-2 and a small Tafel slope of 65 mV dec-1 for HER, and an improved overpotential of 329 mV and a Tafel slope of 107 mV dec-1 for OER. Furthermore, the assembled C@CoP||C@CoP electrolyzer showed excellent overall water splitting performance (1.63 V) at a current density of 10 mA cm-2 and superior durability. This work provides a structure engineering strategy for metal-organic framework (MOF) template-derived hybrids with outstanding electrocatalytic performance.

Keywords: hierarchical nanosheet; metal–organic framework; overall water splitting; transition metal phosphide.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Scheme for fabrication process of C@CoP.
Figure 2
Figure 2
SEM images of (a) Co(OH)2, (b) ZIF-67@Co(OH)2, (c) C@Co3O4, and (d) C@CoP. The insets of (b,d) are TEM images of corresponding materials.
Figure 3
Figure 3
(a) XRD patterns of (1) Co(OH)2, (2) ZIF-67@Co(OH)2, (3) C@Co3O4, and (4) C@CoP. (b) HRTEM image and (c) SAED image of C@CoP. (d) STEM-EDS image and corresponding elemental mapping of C@CoP.
Figure 4
Figure 4
(a) Survey XPS spectra of C@CoP; high-resolution XPS spectra of (b) Co 2p, (c) P 2p, (d) C 1s, (e) O 1s, and (f) N 1 s.
Figure 5
Figure 5
(a) HER polarization curves (inset shows a comparison of their overpotentials at different current densities) and corresponding (b) Tafel plots, (c) linear fitting curves of Cdl, and (d) Nyquist plots for C@CoP and reference materials. (e) Chronopotentiometric responses of C@CoP at different current densities (10–80 mA cm−2). (f) LSV curves of C@CoP before and after 5000-cycle stability test (inset shows the I-t chronoamperometry current curve of C@CoP for 60,000 s at an overpotential of 72 mV).
Figure 6
Figure 6
(a) OER polarization curves (insets show a comparison of their overpotentials at different current densities) and corresponding (b) Tafel plots, (c) linear fitting curves of Cdl, and (d) Nyquist plots for C@CoP and reference materials. (e) Chronopotentiometric responses of C@CoP at different current densities (10–80 mA cm−2). (f) LSV curves of C@CoP before and after 5000-cycle stability test (inset shows the It chronoamperometry current curve of C@CoP for 60,000 s at an overpotential of 329 mV).
Figure 7
Figure 7
(a) Polarization curves of overall water splitting in 1 M KOH for C@CoP||C@CoP and other reference assembled cells. (b) Polarization curves of C@CoP||C@CoP before and after overall water splitting (inset shows the It chronoamperometry current curve of C@CoP||C@CoP for the 60,000 s stability test. (c) The measured and calculated output of H2 and O2 under a current density of 10 mA cm−2 over time. (d) demonstration of an actual water splitting device.

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