TiO2 nanorod arrays decorated with exfoliated WS2 nanosheets for enhanced photoelectrochemical water oxidation

Tungsten Disulfide-Interfacing Nickel-Porphyrin For Photo-Enhanced Electrocatalytic Water Oxidation

Covalent functionalization of tungsten disulfide (WS₂ ) with photo- and electro-active nickel-porphyrin (NiP) is reported. Exfoliated WS₂ interfacing NiP moieties with 1,2-dithiolane linkages is assayed in the oxygen evolution reaction under both dark and illuminated conditions. The hybrid material presented, WS₂ -NiP, is fully characterized with complementary spectroscopic, microscopic, and thermal techniques. Standard yet advanced electrochemical techniques, such as linear sweep voltammetry, electrochemical impedance spectroscopy, and calculation of the electrochemically active surface area, are used to delineate the catalytic profile of WS₂ -NiP. In-depth study of thin films with transient photocurrent and photovoltage response assays uncovers photo-enhanced electrocatalytic behavior. The observed photo-enhanced electrocatalytic activity of WS₂ -NiP is attributed to the presence of Ni centers coordinated and stabilized by the N₄ motifs of tetrapyrrole rings at the tethered porphyrin derivative chains, which work as photoreceptors. This pioneering work opens wide routes for water oxidation, further contributing to the development of non-noble metal electrocatalysts.

Carbon dots dominated photoelectric surface in titanium dioxide nanotube/nitrogen-doped carbon dot/gold nanocomposites for improved photoelectrochemical water splitting

The dynamic behavior of electron-hole pairs at the interface of the nanocomposites is important for photoelectrochemical catalysis, but it is difficult to characterize. Here we construct a ternary titanium dioxide/nitrogen-doped carbon dot/gold (TiO₂/NCD/Au) complex as the model catalyst to investigate the kinetic indexes at their interfaces. Under irradiation (200 mW cm^-2), the photocurrent density of TiO₂/NCD/Au is 10.26 mA cm^-2, which is higher than those of TiO₂/Au (4.34 mA cm^-2), TiO₂/NCD (7.55 mA cm^-2) and TiO₂ (3.34 mA cm^-2). The evolved oxygen of TiO₂/NCD/Au reaches 125.8 μmol after 5000 s test. The energy bands of complexes are very similar to that of the unmodified TiO₂ catalyst due to the low content modification of NCDs and Au. In addition, the transient photovoltage (TPV) tests with a series of control samples show differences about the carriers' separation and transfer process, which verify that Au can increase the separation quantity of electron-hole pairs while NCDs play a more important role on the increase of the separation quantity and separation rate simultaneously. This work quantifies the function of each component in a composite catalyst and deepens the understanding of the catalyst interface design.

Insights into the Operation of Noble-Metal-Free Cocatalyst 1T-WS2 -Decorated Zn0.5 Cd0.5 S for Enhanced Photocatalytic Hydrogen Evolution

Due to inefficient charge separation and low surface catalytic conversion efficiencies, cocatalysts are required for achieving photocatalytic hydrogen evolution. Being a noble-metal-free cocatalyst, metallic 1T-WS₂ with excellent conductivity can function for this reaction. Herein, 1T-WS₂ /Zn_0.5 Cd_0.5 S is constructed via a simple and feasible grinding approach. The composite containing 7.5 % 1T-WS₂ in 1T-WS₂ /Zn_0.5 Cd_0.5 S achieves a hydrogen evolution rate of 61.65 mmol g^-1  h^-1 and an external quantum efficiency of 8.04 % at 420 nm, which is 37 times that of bare Zn_0.5 Cd_0.5 S (1.67 mmol g^-1  h^-1 ). The electrical conductivity of metallic 1T-WS₂ reduces the transfer impedance at the interface and thus accelerates the non-radiative energy transfer and electron transport rate. The different Fermi levels of 1T-WS₂ and Zn_0.5 Cd_0.5 S form a Schottky junction, which promotes the transfer of photogenerated electrons from Zn_0.5 Cd_0.5 S to 1T-WS₂ . More importantly, the close interface contact between 1T-WS₂ and Zn_0.5 Cd_0.5 S results in strong electron interactions, which is conducive to the spatial separation of photogenerated electrons and holes. This work will further expand the application of 1T-WS₂ in the photocatalytic hydrogen evolution process.