Mn-Doped g-C₃N₄ Nanoribbon for Efficient Visible-Light Photocatalytic Water Splitting Coupling with Methylene Blue Degradation

Abstract

The photocatalysis of water-splitting coupling with pollutant degradation was achieved on Mn-doped g-C 3 N 4 nanoribbon (Mn-CNNR) with double purposes of environmental protection and renewable energy production. The photocatalytic efficiency of water splitting using Mn-CNNR-3 in pure water was 2.71 times higher than that using bulk g-C 3 N 4 (CNB) under visible-light illumination. The yields of H 2 and O 2 for Mn-CNNR-3 reached 593.35 μmol/g cat and 59.47 μmol/g cat in methylene blue (MB) solution, and the degradation efficiency of MB simultaneously attained 96.1%. The Mn-CNNR-3 catalyst exhibited good photocatalytic activity after 5 cycles. The D 2 O-tracer experiment proved that H 2 gas was produced by water splitting rather than MB degradation in the photocatalytic system. On the basis of theoretical simulation and measurements, the separation of photogenerated carriers was assuredly promoted by the nanoribbon construction and Mn doping. Meanwhile, by Mn doping, the process from H 2 O 2 to hydroxide radicals on the g-C 3 N 4 surface became beneficial in thermodynamics and experiment, further facilitating the complex photocatalysis. Furthermore, the photocatalytic mechanism was proposed to explain the detailed process of water splitting coupling with MB degradation. The present work sheds light on the design of multifunctional photocatalysts to simultaneously tackle the problems of energy crisis and environmental pollution.

Recent Progress on Carbon Nitride and Its Hybrid Photocatalysts for CO2 Reduction

“…In general, nonmetallic heteroatoms can enter the g‐C 3 N 4 lattice to partially substitute C or N atoms, whereas metallic atoms can insert into the triangular interstitial cavities of g‐C 3 N 4 . Band structure, light absorption ability, and photogenerated electron–hole pairs separation rate of g‐C 3 N 4 can be regulated by doping various nonmetallic atoms such as B, [ 70–72 ] C, [ 73,74 ] O, [ 36 ] P, [ 68 ] S, [ 75 ] and metallic atoms like K, [ 76 ] Na/ Li, [ 77 ] Fe, [ 78 ] Cu, [ 79 ] Mn, [ 80 ] Co, [ 81 ] Mo, [ 82 ] Se, [ 83 ] and so on in g‐C 3 N 4 .…”

Synthesis of Z-scheme Mn-CdS/MoS2/TiO2 ternary photocatalysts for high-efficiency sunlight-driven photocatalysis

“…Because of the negative E CB of CdS-Mn, these electrons exhibit strong reducibility and can easily reduce H þ to H 2 , which agrees well with the results from the experiments of H 2 evolution. The photocatalytic mechanism of water splitting coupling with organic pollutants degradation was proposed as follows 10 Photocatalysts þ hv ! e À þ h þ ð1Þ Á OH þ MO=9 À AC !…”

The high photocatalytic efficiency and stability of LaNiO3/g-C3N4 heterojunction nanocomposites for photocatalytic water splitting to hydrogen

“…Several approaches have been proposed to overcome these problems, such as doping metal (Cu, Al) (15)(16)(17)(18) or metal compound (CdS, NiS, TiO2, BiVO4) (19-23) even non-metal (B, C, N) (24,25), loading noble metal (Au, Pd, Pt) (26) for surface modification. All above measures could effectively promote the separation rate of photo-generated electrons and holes, thus improve the catalytic activities.…”