Hongxing Jia

A cocatalyst-free CdS nanorod/ZnS nanoparticle composite for high-performance visible-light-driven hydrogen production from water

Highly efficient, visible-light-induced hydrogen (H2) production via water splitting can be achieved without the help of a cocatalyst by using a noble-metal-free core–shell photocatalyst, in which zinc sulfide (ZnS) nanoparticles as the protective shell are anchored on the surface of cadmium sulfide nanorods (CdS NRs). Due to the close interfacial contact of component semiconductors, the electronic structure of CdS is strongly coupled with that of ZnS nanoparticles, leading to efficient transfer of charge carriers between them and the improvement of the CdS photostability. The CdS/ZnS NR photocatalyst showed much higher catalytic activity for H2 production than CdS NRs and ZnS under visible light irradiation (λ > 420 nm), which is probably due to fast transfer of the photogenerated charge carriers and/or electron tunneling in the one-dimensional core–shell nanorod structure. Under optimal conditions, the highest hydrogen evolution rate reached 239 μmol h−1 mg−1, which is much greater than ZnS and CdS NRs and also among the best cocatalyst-free photocatalysts for H2 production. The average apparent quantum yield can be achieved as ∼16.8% after 8 h of irradiation (monochromatic light at 420 nm ± 5 nm). A possible mechanism for the photocatalytic reaction based on CdS/ZnS NRs is also discussed.

Green Cobalt Oxide (CoOx) Film with Nanoribbon Structures Electrodeposited from the BF2-Annulated Cobaloxime Precursor for Efficient Water Oxidation

In this study, we report for the first time on the use of a water-soluble BF2-annulated cobaloxime, Co(dmgBF2)2(OH2)2 (Co-DMB, dmgBF2 = difluoroboryl-dimethylglyoxime), as a catalyst precursor for electrocatalytic water oxidation. Oxygen gas bubbles were clearly produced on the FTO electrode at a low overpotential under neutral pH conditions containing Co-DMB. Interestingly, stable green films were produced under these conditions. The current densities can reach to >5 mA/cm(2) at 1.1 V and >10 mA/cm(2) at 1.5 V (vs Ag/AgCl). The morphologies of the films showed nanoribbon structures, which were characterized by scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS).

Pyrolyzed cobalt porphyrin-based conjugated mesoporous polymers as bifunctional catalysts for hydrogen production and oxygen evolution in water

In this present study, a series of cobalt porphyrin-based conjugated mesoporous polymers (CoP-nph-CMP, n = 2, 3, 4) were fabricated as catalyst precursors to generate bifunctional catalysts via pyrolysis (CoP-nph-CMP-800, n = 2, 3, 4) for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Among these catalysts, CoP-2ph-CMP-800 exhibited the best catalytic activity with quite a low overpotential for both the OER (η = 370 mV for 10 mA cm-2) and the HER (η = 360 mV for 10 mA cm-2). Moreover, their excellent bifunctional catalytic performance was also explored in the overall water splitting test (η = 760 mV for 10 mA cm-2).

Cadmium Sulfide Nanorods Decorated with Copper Sulfide via One‐Step Cation Exchange Approach for Enhanced Photocatalytic Hydrogen Evolution under Visible Light

Photocatalytic hydrogen production by means of water splitting has attracted significant attention to convert solar energy into chemical energy. In this present study, a facile one‐step cation exchange approach was used to prepare CuxS decorated on CdS nanorods (CuxS/CdS NRs, x=1–2) for enhanced photocatalytic hydrogen production in water under visible light irradiation (λ>420 nm). Under optimal conditions, the highest H2 production rate achieved was ≈111 μmol h−1 and the apparent quantum yield reached ≈7 %. Efficient transfer processes of photogenerated charge carriers from CdS to CuxS, which can be attributed to the uniform distribution of CuxS on the CdS surface, were confirmed by steady‐state photoluminescence (PL) spectra and time‐resolved photoluminescence spectra. All the results indicate that this low‐cost cation exchange reaction is a promising method to construct an efficient system for photocatalytic hydrogen evolution.

A novel two-dimensional nickel phthalocyanine-based metal–organic framework for highly efficient water oxidation catalysis

Large π-conjugated conductive two-dimensional (2D) metal–organic frameworks (MOFs) via the bottom-up approach have recently emerged as novel and interesting 2D materials. For the first time, herein we demonstrate the design and successful bottom-up fabrication of a novel noble-metal-free nickel phthalocyanine-based 2D MOF (NiPc–MOF) for highly efficient water oxidation catalysis. This NiPc–MOF can be easily grown on various substrates. The thin film deposited on FTO showed high catalytic oxygen evolution reaction (OER) activity with a very low onset potential (<1.48 V, overpotential < 0.25 V), high mass activity (883.3 A g−1), and excellent catalytic durability. To the best of our knowledge, this present 2D MOF film catalyst represents the best OER catalytic activity among molecular catalyst-based materials reported so far. This work represents the first synthesis of a nickel phthalocyanine-based 2D MOF material and application of the π-conjugated 2D MOF for water oxidation.

An iron porphyrin-based conjugated network wrapped around carbon nanotubes as a noble-metal-free electrocatalyst for efficient oxygen reduction reaction

Developing an efficient, robust, and noble-metal-free catalyst for the oxygen reduction reaction (ORR) is crucial for the large-scale commercialization of fuel cells and metal–air batteries. Herein, we report a structurally well-defined iron porphyrin-based conjugated network on carbon nanotubes ((FeP)n-CNTs) as a novel electrocatalyst for the ORR. Its superior electrocatalytic activity toward the ORR is demonstrated by the high-performance catalytic activity of (FeP)n-CNTs with a positive ORR onset potential and half-wave potential (E1/2 ∼ 0.76 V vs. RHE) values as well as outstanding durability and methanol tolerance in alkaline media. In addition, the low H2O2 yield illustrates that the ORR occurs mainly via the direct four-electron (4e−) pathway, and testing shows that the small amount of produced H2O2 can be rapidly consumed through both electrochemical reduction and oxidation. Our results demonstrate that the as-prepared (FeP)n-CNT catalyst is a promising noble-metal-free catalyst for potential applications in fuel cells and metal–air batteries.

A novel symmetrically multifunctionalized dodecamethoxy-cycloparaphenylene: synthesis, photophysical, and supramolecular properties

In the present study, we report the synthesis of a novel symmetrically multifunctionalized cycloparaphenylene (CPP), dodecamethoxy-[9]CPP (ring[9]arene), through nickel-mediated macrocyclization and subsequent reductive aromatization reactions. The electron-donating methoxy groups were introduced onto the curved precursor at an early stage to avoid the problem of non-selective functionalization of CPPs. Compared to [9]CPP, the present dodecamethoxy-[9]CPP shows a significant red shift (>73 nm) in the fluorescence spectrum. In addition, theoretical calculations revealed its increased torsion angles and ring strain (71.01 kcal mol−1) compared with its unsubstituted counterpart.

A Three‐Dimensional Capsule‐like Carbon Nanocage as a Segment Model of Capped Zigzag [12,0] Carbon Nanotubes: Synthesis, Characterization, and Complexation with C70

Herein we report the synthesis and photophysical and supramolecular properties of a novel three-dimensional capsule-like hexa-peri-hexabenzocoronene (HBC)-containing carbon nanocage, tripodal-[2]HBC, which is the first synthetic model of capped zigzag [12,0] carbon nanotubes (CNTs). Tripodal-[2]HBC was synthesized by the palladium-catalyzed coupling of triboryl hexabenzocoronene and L-shaped cyclohexane units, followed by nickel-mediated C-Br/C-Br coupling and subsequent aromatization of the cyclohexane moieties. The physical properties of tripodal-[2]HBC and its supramolecular host-guest interaction with C70 were further studied by UV/Vis and fluorescence spectroscopy. Theoretical calculations revealed that the strain energy of tripodal-[2]HBC was as high as 55.2 kcal mol-1 .