Light excitation has been developed as an economical way to realize room-temperature gas sensing recently. However, the high recombination rate of photogenerated carriers in semiconductor gas sensing materials leads to very limited carriers that can effectively take part in sensing reactions, which greatly restricts the further performance improvement of gas sensing under light excitation. Here, a hierarchical Z-scheme heterostructure microsphere of MoS 2 /SnO 2 is designed and prepared. The heterostructure demonstrates an outstanding NO 2 sensing performance at room temperature with the excitation of a low-power LED light (0.06 W), which exhibits an ultrahigh sensitivity of 264.2 to 10 ppm of NO 2 along with acceptable response/recovery properties. The physical mechanism of NO 2 sensing is analyzed. The results suggest that the construction of the Z-scheme heterostructure between MoS 2 and SnO 2 can greatly promote the separation of photogenerated carriers so that more photogenerated carriers can take part in the NO 2 sensing reaction. Furthermore, the designing of a hierarchically porous structure can provide abundant active sites for gas sensing reactions. The work not only expands the development of Z-scheme heterostructures in gas sensing but also provides a strategy to promote the performance of lightexcited gas sensors by designing a Z-scheme heterostructure with a hierarchically porous structure.
Crystal facet engineering and graphene modification are both effective means to improve the gas sensing performance of metal oxide semiconductors (MOSs) currently. However, research on the crystal facet effect and synergistic effect of graphene modification of p-type MOS sensors is relatively lacking. Here, ptype Co 3 O 4 nanocrystals with controlled crystal facets ({112} and {100}) were in situ wrapped in the two-dimensional (2D) nanosheet network of graphene. It was found that bare {112} facets showed a significantly higher triethylamine sensing performance than {100} facets, implying a strong crystal facet effect. Interestingly, the triethylamine sensing performance of {112} facets was significantly improved after rGO modification, while the performance improvement of Co 3 O 4 {100} was limited after rGO modification. Further study suggested that {112} facets contained more active Co 3+ species and chemically adsorbed oxygen species than {100} facets, which promoted the adsorption of triethylamine and the subsequent sensing reaction. In addition, the strong electronic interaction between Co 3 O 4 {112} crystal facets and rGO promoted efficient charge exchange through the heterogeneous interface. This work provides a new way to improve the gas sensing performance of Co 3 O 4 through the synergistic effect of crystal facet engineering and graphene modification.
Co-based phosphides are considered to be highly promising
electrocatalysts
for both the hydrogen evolution reaction (HER) and oxygen evolution
reaction (OER). However, their electrocatalytic efficiencies are greatly
limited by the weak water dissociation process and unsatisfactory
adsorption ability toward reaction intermediates. Herein, novel Mn-doped
CoP/Ni(PO3)2 heterostructure array electrocatalysts
which are composed of highly dispersed Ni(PO3)2 nanoclusters that are tightly wrapped on Mn-doped CoP nanowire arrays
are designed. An electrocatalytic performance test suggested that
the heterostructure arrays exhibited competitive electrocatalytic
performance toward both HER and OER, which needed overpotentials of
116 and 245 mV to drive a current of 10 mA/cm2, respectively.
Encouragingly, a symmetric two electrode water splitting system constructed
by the heterostructure arrays required an ultralow cell voltage, suggesting
the potential in overall water splitting. First-principles calculations
combined with experimental characterization were further performed
to clarify the electrocatalytic mechanism. On the one hand, effective
doping of Mn atoms could optimize the surface electronic structure
of CoP and promote the intrinsic activity. On the other hand, the
compact and abundant heterogeneous interface between Ni(PO3)2 and CoP not only made more active sites exposed but
also promoted the effective adsorption of intermediate reaction species
on the catalyst surface. This work provides a new strategy to improve
electrocatalytic performance of Co-based phosphides through the synergistic
coupling of metal-doping and phosphate surface decoration, which will
greatly promote the development of highly efficient electrocatalysts
for overall water splitting.
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