Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: Photoelectrochemical (PEC) water splitting is an appealing approach to the hydrogen evolution reaction since it converts sunlight in the form of hydrogen fuel, which has the potential to revolutionize the fossil fuel-based energy systems of the modern society. In the last half century, progress has been made with respect to the material, synthesis, and system. Recent developments of multilayered photoelectrodes have made a breakthrough to improve the sunlight conversion efficiency and strengthen the physiochemical stability. The exploration of new materials for the functional layers of photoelectrodes offers a new opportunity for practical application. Among the emerging materials, metal-free species have shown superior properties, such as high stability, sustainability, and renewability. With respect to inorganic materials, their physiochemical properties can be readily regulated, including thermodynamics and kinetics, and thus increasing attention has been devoted. In this Account, the functional components of a photoelectrodes are specified, namely conductive layers for charge separation and transfer, photocatalytic layers for light absorption, passivation layers for protection of the electrode, and cocatalysts for the acceleration of the surface reaction. We have focused metal-free materials for the functional layers, including the (1) carbon cloth and carbon quantum dots (CQDs) for the conductive layer, 2) polymeric carbon nitrides (PCNs), carbon doped boron nitride, and covalent organic frameworks for photocatalytic layers, and (3) CQDs and black phosphorene for cocatalysts. We aim to identify the relationship between the function of the metal-free materials and the performance of the water splitting reaction. With respect to the outlook, discussions have been presented for the further development of metal-free materials to improve the performance of each functional layer. Despite the fact that the use of metal-free materials for PEC water splitting is still in its infancy, this Account not only provides new thoughts and opportunities to pursue an improved performance for the water-splitting reaction but also stimulates advanced applications by using metal-free PEC systems.

show abstract

Section: Junctional-structured Photocatalytic Layer By Metal-free Mat...mentioning

confidence: 99%

Roles of Metal-Free Materials in Photoelectrodes for Water Splitting

Wang

Fang

et al. 2021

Acc. Mater. Res.

View full text Add to dashboard Cite

show abstract

“…The XRD patterns of the obtained CN electrodes (Figure 3a) exhibit two typical CN signals corresponding to an in-plane (100) diffraction at 12.8° and an interplanar stacking (002) diffraction at 27.6°. [36] The FTIR spectra of the CN electrodes (Figure S4, Supporting Information) show signals in the 1100-1700 cm −1 range that correspond to CN heterocycles stretching modes. The peaks at ≈800 cm −1 are attributed to the breathing vibration of the heptazine units in CN films, whereas the broad bands at ≈3000-3600 cm −1 match the stretching vibration of NH in the amino groups resulting from incomplete polymerization.…”

Section: Preparation and Characterization Of Cn Filmsmentioning

confidence: 99%

Mediated Growth of Carbon Nitride Films via Spray‐Coated Seeding Layers for Photoelectrochemical Applications

Tashakory

Karjule

Abisdris

et al. 2021

Advanced Sustainable Systems

Self Cite

View full text Add to dashboard Cite

Polymeric carbon nitride (CN) has emerged as a promising semiconductor in photoelectrochemical devices, thanks to its unique electronic and catalytic properties, low price, stability in various chemical environments, and benign nature. Decent progress in the deposition and growth of CN layers on substrates has been achieved using several deposition and growth methods; however, the properties of the layer, including the quality of its contact with the substrate and its structural properties, are still largely dependent on the surface properties of said substrate. Here, a new approach is introduced in which a spray‐coated seeding layer composed of CN monomers directs the growth of a homogenous, thick CN layer on a substrate by calcination at high temperature in the presence of melamine vapor. Uniform CN layers with strong adhesion to the substrate are obtained. The influence of the seeding layer and the vapor composition on the photoelectrochemical, optical, and structural properties is studied in detail. The best‐performing electrode, based on urea as the seeding layer, demonstrates good activity as a photoanode in photoelectrochemical cells, reaching up to 300 µA cm−2 in the presence of a hole scavenger.

show abstract

“…It has been a little more than a decade since polymeric carbon nitride (PCN, otherwise known as melon, C3N4 polymer or g-C3N4) has been introduced as a novel type of solid photocatalyst. 1 Its chemical and thermal stability, low cost, non-toxicity and exceptional photocatalytic performance have made it an object of studies of light-driven selective redox transformations [2][3][4][5][6][7][8][9][10][11][12] and pollutant degradation, [13][14][15] solar cells research 16,17 and, owing to its suitable valence (VB) and conduction (CB) bands positions, 1,[18][19][20][21][22][23] especially of photocatalytic H2 production from aqueous suspensions. 1,20,[24][25][26][27] However, many of these applications, in particular the generation of solar fuels and other high-value compounds, 28 would profit from operating the PCN within a proper photoelectrochemical (PEC) cell setup, affording thus more efficient charge separation and product isolation.…”

Section: Introductionmentioning

confidence: 99%

“…38,39,41,44 As an alternative approach, the direct PCN growth on conductive substrates was also proposed. 31, [45][46][47][48][49] Since PCN itself was not soluble in any of the tested organic solvents, its precursors were used to grow a layer on the substrate via high-temperature condensation, a notoriously uncontrollable process, leading to the tens of micrometers thick films composed of large loose particles. Such films typically exhibited suboptimal mechanical and photo-operational stability, which was demonstrated by the detachment of PCN particles from the film under sonication and pronounced selfphotooxidation revealed by low Faradaic efficiencies towards the reaction products.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

Adler¹,

Krivtsov²,

Mitoraj³

et al. 2020

Preprint

View full text Add to dashboard Cite

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for photoelectrochemical (PEC) applications, the fabrication of highly stable and photoactive PCN photoelectrodes has been a largely elusive goal to date. Here we tackle this challenge by devising, for the first time, a sol–gel approach that enables facile preparation of photoanodes based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol–gel process capitalizes on the use of a water-soluble PHI precursor composed of nanosized (~10 nm) particles that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on a conductive substrate resulting in formation of mechanically stable porous polymeric thin layers (~400 nm), in contrast to the commonly obtained loosely attached thick particulate coatings. The resulting photoanodes exhibit unprecedented PEC performance in methanol reforming in neutral pH electrolytes with very high photocurrents of 177±27 mA (1 sun illumination) cm<sup>-2</sup> and 320±40 mA cm<sup>-2</sup> (2 sun illumination) at 1.23 V vs. RHE, with very high photocurrents down to ~0 V vs. RHE. These parameters permit effective operation even without any external electric bias, as demonstrated by zero-bias photoreforming of methanol and glycerol, and highly selective (~100%) photooxidation of 4-methoxybenzyl alcohol (4-MBA). The robust binder-free films derived from sol–gel processing of water-soluble PCN thus represent a new paradigm for high-performance ‘soft-matter’ photoelectrocatalytic systems based on PCN.

show abstract

Controllable Synthesis of Carbon Nitride Films with Type-II Heterojunction for Efficient Photoelectrochemical Cells

Cited by 46 publications

References 61 publications

Roles of Metal-Free Materials in Photoelectrodes for Water Splitting

Roles of Metal-Free Materials in Photoelectrodes for Water Splitting

Mediated Growth of Carbon Nitride Films via Spray‐Coated Seeding Layers for Photoelectrochemical Applications

Sol–Gel Processing of Water-Soluble Carbon Nitride Enables High-Performance Photoanodes

Contact Info

Product

Resources

About