Dopant and Defect Doubly Modified CeO2/g‑C3N4 Nanosheets as 0D/2D Z‑Scheme Heterojunctions
for Photocatalytic Hydrogen Evolution: Experimental and Density Functional
Theory Studies
posted on 2021-08-18, 16:41authored byShouwei Zhang, Jinghua Guo, Weijie Zhang, Huihui Gao, Jinzhao Huang, Gang Chen, Xijin Xu
Exploring
novel 2D heterojunction photocatalysts with a wide spectral
response and high active site exposure has been a huge challenge.
A small-sized catalyst with high dispersibility has been considered
an ideal model for maximizing active sites and increasing atomic efficiency.
Herein, the 0D/2D Z-scheme heterojunction was designed by in situ
solvothermal and subsequent calcination in air by integrating dopant
and defect doubly modified CeO2 nanodots and g-C3N4 nanosheets (CNNS). Ultrafine cobalt-doped CeO2 nanodots (≈4 to 5 nm) with enriched oxygen vacancies (Co-CeO2–OVs) were uniformly and tightly anchored on the surface
of CNNS to form a heterojunction. The density functional theory (DFT)
calculations confirmed that cobalt dopants and oxygen vacancies form
impurity energy states at the top of a valence band, thus narrowing
the band gap. The optimized 0D/2D heterojunction showed a remarkable
hydrogen production rate of ∼203.6 μmol/h, which was
approximately 4.9- and 30.8-fold higher than that of CNNS (∼41.2
μmol/h) and CeO2 (∼6.6 μmol/h), respectively.
Moreover, a large quantum yield of ∼8.94% was achieved at 420
nm. The 0D/2D heterojunction with a larger intimate area provided
abundant reactive active sites and strong electron interactions to
excite photogenerated carrier dynamics, and the doping and defect
engineering could expand the light response range by regulating the
electronic band structure. Strong evidence provided by experimental
results and DFT calculations proved the Z-scheme charge transfer pathway.
This work not only provided a novel approach to integrate 0D nanodots
and 2D nanosheets for the formation of intimate Z-scheme heterointerfaces
but also deepened the understanding of the dopant–defect synergistic
modification to optimize the band structure and electronic structures
for high-efficient solar energy capture and conversion.