Highly Efficient Photocatalytic H₂ Evolution from Water using Visible Light and Structure‐Controlled Graphitic Carbon Nitride

Abstract

The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low-cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported. The g-C3N4 exhibits an extraordinary hydrogen-evolution rate (ca. 20 000 μmol h−1 g−1 under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 % under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced.

Modelling materials for solar fuel synthesis by artificial photosynthesis; predicting the optical, electronic and redox properties of photocatalysts

“…The most well-known of these photocatalysts are the inorganic solids [1][2][3]6], mostly oxides but also sulfides and selenides, the former including titanium dioxide [13][14][15], the quintessential photocatalyst. Perhaps less well-known, a range of supramolecular systems [16,17] and even organic polymers [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] have also been reported to act as photocatalysts. In this mini-review we will discuss computational work on modelling such photocatalysts in terms of the relevant material properties and processes, as well as what we believe to be key aspects to consider when performing such calculations.…”

Precise Formation of a Hollow Carbon Nitride Structure with a Janus Surface To Promote Water Splitting by Photoredox Catalysis

“…These results indicate afierce interaction between the HCNS and cocatalysts of Co 3 O 4 and Pt NPs. [18] Thep hotoluminescence (PL) spectra in Figure 2b show astrong emission peak, which is assigned to the recombination of the electron-holes. This recombination process can be suppressed by introducing Co 3 O 4 and Pt NPs that are randomly distributed on the outer surfaces of the HCNS.F or the Co 3 O 4 /HCNS/Pt sample,t he otherwise strong PL is greatly quenched.…”

High-Yield Synthesis of Carbon Nitride with Improved Photocatalytic Performance

“…Martin DJ et al investigated the hydrogen evolution activities of carbon nitride synthesized from urea, dicyandiamide and thiourea under identical conditions, respectively. 33 According to the hydrogen evolution measurement, the urea-derived carbon nitride exhibited the highest hydrogen evolution efficiency. However, only the same synthesis condition of the different precursors is considered in these studies.…”

“…However, only the same synthesis condition of the different precursors is considered in these studies. 12,[32][33][34] In fact, not only the precursors but also the different pyrolysis conditions have great effects on the photocatalytic performance of carbon nitride due to different thermal decomposition temperature of precursors which could lead to various morphology, band gap, surface area and yields. In present work, we systemically analyze the advantages and disadvantages of carbon nitride prepared from four frequently-used precursors including urea, thiourea, dicyandiamide and melamine, respectively.…”