Graphitic Carbon Nitride Structures on Carbon Cloth Containing Ultra- and Nano-Dispersed NiO for Photoactivated Oxygen Evolution

The development of low-cost and high-efficiency oxygen evolution reaction (OER) photoelectrocatalysts is a key requirement for H2 generation via solar-assisted water splitting. In this study, we report on an amenable fabrication route to carbon cloth-supported graphitic carbon nitride (gCN) nanoarchitectures, featuring a modular dispersion of NiO as co-catalyst. The synergistic interaction between gCN and NiO, along with the tailoring of their size and spatial distribution, yield very attractive OER performances and durability in freshwater splitting, of great significance for practical end-uses. The potential of gCN electrocatalysts containing ultra-dispersed, i. e. "quasi-atomic" NiO, exhibiting a higher activity than the ones containing nickel oxide nanoaggregates, is further highlighted by their activity even in real seawater. This work suggests that efficient OER catalysts can be designed through the construction of optimized interfaces between transition metal oxides and carbon nitride, yielding inexpensive and promising noble metal-free systems for real-world applications.

Polymer Photoelectrodes for Solar Fuel Production: Progress and Challenges

Converting solar energy to fuels has attracted substantial interest over the past decades because it has the potential to sustainably meet the increasing global energy demand. However, achieving this potential requires significant technological advances. Polymer photoelectrodes are composed of earth-abundant elements, e.g. carbon, nitrogen, oxygen, hydrogen, which promise to be more economically sustainable than their inorganic counterparts. Furthermore, the electronic structure of polymer photoelectrodes can be more easily tuned to fit the solar spectrum than inorganic counterparts, promising a feasible practical application. As a fast-moving area, in particular, over the past ten years, we have witnessed an explosion of reports on polymer materials, including photoelectrodes, cocatalysts, device architectures, and fundamental understanding experimentally and theoretically, all of which have been detailed in this review. Furthermore, the prospects of this field are discussed to highlight the future development of polymer photoelectrodes.

Recent Progress on Photoelectrochemical Water Splitting of Graphitic Carbon Nitride (g-CN) Electrodes

Graphitic carbon nitride (g-CN), a promising visible-light-responsive semiconductor material, is regarded as a fascinating photocatalyst and heterogeneous catalyst for various reactions due to its non-toxicity, high thermal durability and chemical durability, and "earth-abundant" nature. However, practical applications of g-CN in photoelectrochemical (PEC) and photoelectronic devices are still in the early stages of development due to the difficulties in fabricating high-quality g-CN layers on substrates, wide band gaps, high charge-recombination rates, and low electronic conductivity. Various fabrication and modification strategies of g-CN-based films have been reported. This review summarizes the latest progress related to the growth and modification of high-quality g-CN-based films. Furthermore, (1) the classification of synthetic pathways for the preparation of g-CN films, (2) functionalization of g-CN films at an atomic level (elemental doping) and molecular level (copolymerization), (3) modification of g-CN films with a co-catalyst, and (4) composite films fabricating, will be discussed in detail. Last but not least, this review will conclude with a summary and some invigorating viewpoints on the key challenges and future developments.

P5W30/g-C3N4 heterojunction thin film with improved photoelectrochemical performance for solar water splitting

For the first time, to design a new photocatalyst, a Preyssler-type polyoxometalate was composited with g-C₃N₄ to improve its photoelectrochemical performance.

NiO nanowires as hole-transfer layer for drastic enhancement of CdSe-sensitized photocathodes

Grass-like NiO nanowires as a hole-transfer layer to improve light capture efficiency and charge transfer rate for a CdSe-sensitized photocathode.

Visible-Light-Driven Photocatalytic Activity of SnO2-ZnO Quantum Dots Anchored on g-C3N4 Nanosheets for Photocatalytic Pollutant Degradation and H2 Production

A zero-dimensional/two-dimensional heterostructure consists of binary SnO₂-ZnO quantum dots (QDs) deposited on the surface of graphitic carbon nitride (g-C₃N₄) nanosheets. The so-called SnO₂-ZnO QDs/g-C₃N₄ hybrid was successfully synthesized via an in situ co-pyrolysis approach to achieve efficient photoactivity for the degradation of pollutants and production of hydrogen (H₂) under visible-light irradiation. High-resolution transmission electron microscopy images show the close contacts between SnO₂-ZnO QDs with the g-C₃N₄ in the ternary SnO₂-ZnO QDs/g-C₃N₄ hybrid. The optimized hybrid shows excellent photocatalytic efficiency, achieving 99% rhodamine B dye degradation in 60 min under visible-light irradiation. The enriched charge-carrier separation and transportation in the SnO₂-ZnO QDs/g-C₃N₄ hybrid was determined based on electrochemical impedance and photocurrent analyses. This remarkable photoactivity is ascribed to the "smart" heterostructure, which yields numerous benefits, such as visible-light-driven fast electron and hole transfer, due to the strong interaction between the SnO₂-ZnO QDs with the g-C₃N₄ matrix. In addition, the SnO₂-ZnO QDs/g-C₃N₄ hybrid demonstrated a high rate of hydrogen production (13 673.61 μmol g^-1), which is 1.06 and 2.27 times higher than that of the binary ZnO/g-C₃N₄ hybrid (12 785.54 μmol g^-1) and pristine g-C₃N₄ photocatalyst (6017.72 μmol g^-1). The synergistic effect of increased visible absorption and diminished recombination results in enhanced performance of the as-synthesized tin oxide- and zinc oxide-modified g-C₃N₄. We conclude that the present ternary SnO₂-ZnO QDs/g-C₃N₄ hybrid is a promising electrode material for H₂ production and photoelectrochemical cells.

Novel composites of graphitic carbon nitride and NiO nanosheet arrays as effective photocathodes with enhanced photocurrent performances

Novel composites composed of graphitic carbon nitride (GCN) and p-type semiconductor of NiO nanosheet arrays were fabricated for the first time and demonstrated to be efficient photocathodes for enhancing charge separation and hole transfer.