Porphyrin-Modified Cobalt Sulfide as a Developed Noble Metal-free Photoelectrocatalyst toward Methanol Oxidation under Visible Light

Abstract

Designing noble metal-free electrocatalysts with highly efficient performance toward methanol oxidation reaction (MOR) still remains a significant challenge. Herein, 5,10,15,20-tetrakis­(4-carboxylphenyl) porphyrin (TCPP) was used as a photosensitive organic molecule to modify cobalt sulfide (CoS) nanosheets, which exhibit a higher catalytic activity toward MOR than pure CoS under visible irradiation. Photoluminescence emission spectra and UV–vis diffuse reflectance spectra (DRS) reveal the catalytic mechanism from the synergetic effect from porphyrin molecules and CoS nanosheets because the recombination of photoelectrons and holes of the nanocomposites is remarkably inhibited and then electron transfer is accelerated. Notably, TCPP–CoS exhibits the high mass activity of 1240 mA mg–1 for MOR irradiated by visible light, which is 1.43 times that of pure CoS. This work opens up a feasible and practical pathway for designing highly efficient noble metal-free MOR photoelectrocatalysts.

Noble Metal‐Free CoSx/NiSx Heterojunction for Photo‐Assisted Methanol Electrooxidation

“…When the CoS x /NiS x heterojunction adsorb light under the light irradiation, the e − and h + generated in conduction band and valence band (R1). The h + and e − can react with surface adsorbed OH − /H 2 O and O 2 to form strong oxidative OH⋅ [12c,28] and O 2 − ⋅ [26,29] respectively on the surface of CoS x /NiS x heterojunction (R2 and R3). The OH⋅, O 2 − ⋅and h + will increase the oxidizing rate of the methanol and intermediate (formaldehyde, formic acid and CO ads ), resulting an efficiently poisoning suppression (R5–R9) [27–28] .…”

“…The h + and e − can react with surface adsorbed OH − /H 2 O and O 2 to form strong oxidative OH⋅ [12c,28] and O 2 − ⋅ [26,29] respectively on the surface of CoS x /NiS x heterojunction (R2 and R3). The OH⋅, O 2 − ⋅and h + will increase the oxidizing rate of the methanol and intermediate (formaldehyde, formic acid and CO ads ), resulting an efficiently poisoning suppression (R5–R9) [27–28] . On the other hand, the photogenerated e − transferred to the circuit by external electric field, thus preventing the recombination of e − ‐h + pairs, this is an efficient strategy for enhancing the photocatalysis efficiency.…”

“…(formaldehyde, formic acid and CO ads ), resulting an efficiently poisoning suppression (R5-R9). [27][28] On the other hand, the photogenerated e À transferred to the circuit by external electric field, thus preventing the recombination of e À -h + pairs, this is an efficient strategy for enhancing the photocatalysis efficiency.…”

Catalytic hydrodeoxygenation of biomass-derived pyrolysis oil over alloyed bimetallic Ni3Fe nanocatalyst for high-grade biofuel production

“…Based on this study and previous work described elsewhere, a conversion mechanism for the photoelectrocatalytic reduction of CO2 to CH3OH is schematically depicted in Figure 4e. [7][8][9][10][11][12][13]16 In this mechanism. Several basic steps are involved in the PEC reduction of CO2 to CH3OH over the Au/α-Fe2O3/RGO photocathode and Ru/RGO-modified Pt anode at -0.6 V in 0.1 KOH electrolyte solution.…”

“…The PECs, which connect a metallic anode for water oxidation (2H2O → O2 + 4H + ) to produce O2 along with protons (H + ), and a p-type photocathode could produce sufficient photogenerated electrons over a wide range of solar light wavelengths; thus, the produced H + and ecan effectively participate in the reduction of CO2 at the cathode surface. 5 Usually, various nanostructured p-type semiconductors and their composites, including Cu NP/f-RGO/CF, 6 CuFe2O4@PANI, 7 Au NP-modified glass carbon electrodes, 8 porphyrin-modified cobalt sulfide, 9 CuBi2O4/TiO2-NTs, 10 Pt-modified TiO2 nanotubes, 11 CuO/g-C3N4, 12 GO−CuFe2O4, 13 Ag/Cu2O/CuO electrodes, 14 S-TiO2@GS, 15 CuBi2O4/TiO2-NTs, 10 worm-like FeS2/TiO2 nanotubes, 16 Cu@porphyrin-COFs nanorods, 17 TiO2NT@PDA electrodes, 18 Pd-Cu cathodes, 19 ZnO:rGO-Cu:Cu2O, 20 Cu/Cu2O-Cu(BDC-NH2), 21 and FTO/Cu/Bi2Se3-Se/Cu2O electrodes 22 , were successfully used as the photocathode or photoanode for PEC CO2 reduction for fuel production.…”