3.4 Brunauer-Emmett-Teller analysis
The Brunauer-Emmett-Teller (BET) specific surface area
(S BET) and
the pore diameter distribution of
ZnCdS nanoparticles, CoP
polyhedrons, Co3O4 QDs and
bi-heterostructured O/ZCS/P-3 cages were analyzed by N2adsorption-desorption measurements as displayed in Fig. 5. The type IV
isotherms with type H3 hysteresis loops in Fig. 5a and the pore diameter
distribution curves in Fig. 5b indicate the presence of mesoporous
structure in the four as-synthesized photocatalysts, which will
facilitate the mass transfer for heterogeneous catalysis [41]. And
the average pore size of ZnCdS
nanoparticles, CoP polyhedrons, Co3O4QDs and O/ZCS/P-3 is 20, 18, 4 and 22 nm, respectively. In comparison
with CoP polyhedrons and Co3O4 QDs,
ZnCdS nanoparticles possess a relatively small surface area of 30
m2·g-1 owing to its relatively
larger density. However, an enlarged BET
surface area of 37
m2·g-1 for hierarchical O/ZCS/P-3
bi-heterostructure cages was gained because of the integration of both
CoP (79 m2·g-1) polyhedrons and
Co3O4 QDs
(178
m2·g-1) with ZnCdS nanoparticles,
which ensures more active sites for photocatalytic hydrogen evolution
reaction.