Charge kinetics plays a vital role in determining the quantum efficiency of solar-to-chemical conversion in photocatalysis. For most layered compounds, the photocatalytic performance is largely hindered by its sluggish charge transfer kinetics. Herein, we propose a novel strategyheteroatom-mediated spatial charge separation and transfer-to accelerate photogenerated charge kinetics for boosting the photocatalytic performance of graphitic carbon nitride (CN). Both the experimental results and first-principle calculations show that out-of-plane charge transport and in-plane charge separation within CN nanosheets can be accelerated via F intercalation and B intralayer modification. The B implantation could realize in-plane charge-separation by spatial separation of HOMO and LUMO to promote efficient exciton dissociation, and the F heteroatom, as interlayer electron channel, accelerates the out-of-plane oriented charge transport. The visible-light photocatalytic activity of codoped CN nanosheets is greatly boosted via modulating the charge kinetics, which can be demonstrated by degrading methyl orange and colorless phenol as models. Moreover, the samples exhibit excellent photo-electrocatalysis OER activity, outperforming the metal CoSe 2 catalyst. The enhanced catalytic activities are attributed to synergistically utilizing 2D ultrathin structural advantage and accelerating charge kinetics. This work proposes a novel strategy to tune charge carrier separations and migrations in functionalized 2D layered materials for environmental catalysis and advanced energy.
HighlightsA novel heteroatom-mediated spatial charge separation and transfer strategy is proposed in B/F codoped CN nanosheets.Both the experimental results and first-principle calculations show that photogenerated charge kinetics can be accelerated within B/F codoped CN nanosheets.The B implantation could realize in-plane charge-separation by spatial separation of HOMO and LUMO to promote efficient exciton dissociation.The F heteroatom, as interlayer electron channel, accelerates the out-of-plane oriented charge transport.
BACKGROUND: Sustainable production of oxygen and hydrogen via catalyst-aided water splitting utilizing solar energy has attracted increasing interest. The primary issue in this field is the development of earth-abundant and active photoelectrocatalytic materials. Herein, a novel hierarchical g-C 3 N 4 /g-C 3 N 4 metal-free homojunction catalyst is synthesized through partial hydrolysis of melamine in alkali and subsequent thermal treatment.RESULTS: The hierarchical g-C 3 N 4 /g-C 3 N 4 metal-free homojunction composed of lamellas features large exposed surface area, abundant interface contact and more channels for mass transfer, making it highly effective for water splitting with a small overpotential of 500 mV at 10 mA cm −2 and low Tafel slope of 93.1 mV dec −1 for oxygen evolution reaction (OER) in 1.0 mol L −1 potassium hydroxide (KOH) solution, as well as 259 mV at 10 mA cm −2 and 109.33 mV dec −1 for hydrogen evolution reaction (HER) in 0.5 mol L −1 sulfuric acid (H 2 SO 4 ) solution. Furthermore, the overpotential and Tafel slope further decrease to 383.4 mV and 69.52 mV dec −1 for OER, 150.1 mV and 67.93 mV dec −1 for HER upon visible light irradiation, demonstrating the exceptional photo-responsive catalytic performance, which can be attributed to the direct Z-scheme homojunction resulting in effective charge transfer and •OH and superoxide free radicals produced under visible light irradiation.CONCLUSION: This work provides a facile but effective approach for the construction of metal-free OER/HER bifunctional catalyst with high photo-responsive performance, achieving higher activity for catalyst-assisted water splitting.
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