Ultrathin MOF Coupling with Molecular Cobaloxime to Construct an Efficient Hybrid Hematite Photoanode for Photocatalytic Water Splitting

Abstract

It is a great challenge to develop efficient artificial photosynthesis systems by mimicking natural photosynthesis. In this present work, an organo-inorganic hybrid photoanode was fabricated by depositing ultrathin NiFe MOF nanolayers and molecular cobaloxime cocatalyst on the surface of Ti-doped porous hematite (Ti-PH). This hybrid photoanode exhibited a high photocurrent density of 2.45 mA/cm 2 at 1.23 V vs the reversible hydrogen electrode (RHE) under AM 1.5 G illumination with excellent stability. Moreover, the optimal incident photon-to-current efficiency (IPCE) of the hybrid photoanode reached 83.0% at 365 nm and the surface charge injection efficiency (η inj ) was improved to 87.5% at 1.23 V vs RHE. Detailed investigations reveal that NiFe MOFs can effectively facilitate charge separation as a hole-transport layer and molecular cobaloxime cocatalyst can passivate surface trap states to increase water oxidation kinetics.

Photocatalytic Conversion of Formic Acid to Syngas (CO + H2) and Methane with Homogeneous Molecular Cobaloxime Catalysts

“…Two sharp peaks at 796.4 and 781.4 eV can be attributed to Co 2p 1/2 and Co 2p 3/2 , respectively, and the other two broad peaks are satellite peaks, which fit the peaks of typical cobaloxime molecules. The high-resolution C 1s spectrum of the hybrid sample exhibited three obvious peaks at 288.3, 286.1, and 284.7 eV, as shown in Figure d, corresponding to CO, C–O, and CC in the cobaloxime molecules, respectively. , …”

“…The high-resolution C 1s spectrum of the hybrid sample exhibited three obvious peaks at 288.3, 286.1, and 284.7 eV, as shown in Figure 2d, corresponding to C�O, C−O, and C�C in the cobaloxime molecules, respectively. 37,38 The photocatalytic activities of cobaloxime complexes 1−4 for CH 4 production from HCOOH were studied under visible light in a 6 M formic acid solution (pH 3.5) containing 0.08 mM cobaloxime, 50 vol % CH 3 CN for dissolution, and 2 mg of CdS NRs, as shown in Figure 3a. All the photocatalytic systems containing cobaloxime complexes 1−4 showed methane production from formic acid decomposition.…”

Few‐Layer Fullerene Network for Photocatalytic Pure Water Splitting into H2 and H2O2

“…In Figure 4a, the few-layer C 60 nanosheet sample shows arcs of smaller curvature compared to the bulk sample, indicating a faster charge-transfer process. [21] The photocurrent comparison between bulk Mg 4 C 60 and few-layer samples is shown in Figure 4b. The photocurrent of the few-layer C 60 nanosheets is much higher than that of bulk Mg 4 C 60 , suggesting a more efficient charge-separation process.…”

“…Electrochemical impedance spectroscopy (EIS) measurements were carried out under visible light to characterize the charge‐transport performance of the bulk Mg 4 C 60 and few‐layer samples. In Figure 4a, the few‐layer C 60 nanosheet sample shows arcs of smaller curvature compared to the bulk sample, indicating a faster charge‐transfer process [21] . The photocurrent comparison between bulk Mg 4 C 60 and few‐layer samples is shown in Figure 4b.…”

The Journal of Physical Chemistry C Virtual Special Issue on “Energy and Catalysis in China”

“…(3) Synthesis of fine chemicals: selective reduction of nitrobenzene on iron and nitrogen cofunctionalized carbon materials or PtPdCu/Al 2 O 3 , hydrogenation of quinoline and benzoic acid on RhPt/MCM-41, hydroformylation of diisobutene on CoFe alloy catalysts, and selective hydrogenation of cinnamaldehyde to cinnamyl alcohol on Pt@Fe-CeO 2 catalysts or Pt/TiO 2 . Photocatalysis can directly convert solar energy into chemical energy, and two important photocatalytic reactions are included in this VSI: photocatalytic water splitting on Au nanoparticles embedded in g -C 3 N 4 , BiVO 4 , Ta 3 N 5 , SnNb 2 O 6 nanoplates, silicon material, MoO 3 –ZnIn 2 S 4 , carbon nitride, NiFe metal–organic framework (MOF) and cobaloxime-modified Ti-doped hematite, and photocatalytic CO 2 conversion on α-Fe 2 O 3 /CdS heterostructures, CdSe/CdSe x S 1– x /CdS alloyed quantum dots/TiO 2 , AgTaO 3 , perylene diimide/graphene- g -C 3 N 4 , P-doped ZnIn 2 S 4 , MCo 2 O 4−δ (M = Zn, Ni, Cu), and PtRu/TiO 2 . A few other photocatalytic reactions, such as the selective oxidation of cyclohexane to cyclohexanone on In 2 O 3 /N-doped TiO 2 , the reduction of aromatic nitro compounds on Ag/Ag x S, and NO removal on Ba-doped BiOBr, are also discussed.…”