Recently, metal-free graphitic carbon nitride (g-C3N4) has been recognized as a potential candidate for high-performance photocatalytic hydrogen production while challenges still remain due to poor electronic properties and limited surface active sites. We demonstrate that g-C3N4 can be simultaneously co-doped with S, P and O nonmetal-atoms and exfoliated into ultrathin 2D nanosheets with a thickness of ∼3 nm by a simple, sequential thermal synthesis. The multi-atoms doping and nanostructure modulation remarkably enhanced the photocatalytic hydrogen production under illumination, with the optimal H2 evolution rate reaching 2480 μmol g−1 h−1. First-principle calculations and experimental evidences suggest that, upon elemental doping within the g-C3N4 framework, S atoms occupied the interstitial sites and P and O atoms replaced the C and N atoms, respectively. Consequently, photo-induced charge transfer and separation significantly improved owing to the construction of a more favorable charge transfer pathway. Furthermore, introducing heteroatoms into the structure of g-C3N4 narrowed the bandgap and negatively shifted the conduction band edge, leading to extended visible-light absorption and stronger electron reducibility for subsequent H2 production. Importantly, the in-situ generated 2D g-C3N4 nanosheets exhibited more catalytic surface sites, which was highly beneficial to the photocatalytic water splitting.

Unveiling the origin of boosted photocatalytic hydrogen evolution in simultaneously (S, P, O)-Codoped and exfoliated ultrathin g-C3N4 nanosheets

Exploring active catalyst materials for solar-driven photocatalytic water splitting into oxygen has proven extremely challenging, mostly due to poor oxygen-evolving efficiency originating from intrinsically sluggish oxygen evolution reaction (OER) kinetics. Ag3PO4 has been actively pursued as a promising photocatalyst for oxygen evolution from water-splitting. However, its low OER efficiency is a long standing problem. Both the construction of Z-scheme Ag3PO4-based composite photocatalytic systems and the optimization of surface morphology and interfacial contact in heterojunctions photocatalysts would be beneficial for boosting OER efficiency. Here we report on the fabrication of Ag3PO4/fish scale-like graphitic carbon nitride (g-C3N4) sheet composites with well-defined heterostructures and intimate interfacial contact driven by electrostatic assembly. The Ag3PO4/modified g-C3N4 composites photocatalyst reveals significantly enhanced oxygen-evolving activity under light-emitting diode (LED) illumination. Effective surface modification of g-C3N4, strong interfacial interactions between two semiconductors and tandem Z-scheme-type pathway for more efficient charge transfer synergistically accelerates the redox capability of Ag3PO4 for OER. This work may provide new insights into the design and construction of high-performance solar-driven Z-scheme photocatalytic water splitting systems.

Interfacial optimization of g-C3N4-based Z-scheme heterojunction toward synergistic enhancement of solar-driven photocatalytic oxygen evolution

Recent advances in g-C3N4-based heterojunction photocatalysts

Oxamide-modified g-C3N4 nanostructures: Tailoring surface topography for high-performance visible light photocatalysis

The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their quantum efficiencies for hydrogen production from visible photons remain too low for the large scale deployment of this technology. Visible light absorption and efficient charge separation are two key necessary conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon frameworks and their composites have emerged as potential photocatalysts due to their astonishing properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption, high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields. The feasibility of structural and chemical modification to optimize visible light absorption and charge separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution.

X.G. Cui

Papers

Fabrication of dual direct Z-scheme g-C3N4/MoS2/Ag3PO4 photocatalyst and its oxygen evolution performance

Solar photocatalytic water oxidation over Ag 3 PO 4 /g-C 3 N 4 composite materials mediated by metallic Ag and graphene

Fabrication of modified g-C3N4 nanorod/Ag3PO4 nanocomposites for solar-driven photocatalytic oxygen evolution from water splitting

Surface oxidation phenomenon and mechanism of AISI 304 stainless steel induced by Nd:YAG pulsed laser

Microstructure and microhardness of fiber laser butt welded joint of stainless steel plates