Abstract:
Development of heterostructured photocatalysts which can facilitate spatial separation of
photo-generated charge carriers is crucial for achieving improved photocatalytic H2 production.
Consequently, herein, we report the synthesis of Zn0.5Cd0.5S/Ni2P heterojunction
photocatalysts with varying amount of Ni2P, 0.5 (S1), 1 (S2), 3 (S3), 5 (S4) and 10wt% (S5) for
the efficient visible-light-assisted H2 generation by water splitting. The heterostructures
were characterized thoroughly by PXRD, FE-SEM, EDS, HR-TEM and XPS studies. FE-SEM
and HR-TEM analyses of the samples unveiled the presence of Zn0.5Cd0.5S microspheres
composed of smaller nanocrystals with the surface of the microspheres covered with Ni2P
nanosheets and the intimate contact between the Zn0.5Cd0.5S and the Ni2P. Further, visiblelight-
assisted photocatalytic investigation of the samples showed excellent water splitting
activity of the heterostructure, Zn0.5Cd0.5S/1wt%Ni2P (S2) with very high H2 generation rate
of 21.19 mmol h 1g 1 and the AQY of 21.16% at 450 nm with turnover number (TON) and
turnover frequency (TOF) of 251,516 and 62,879 h 1 respectively. Interestingly, H2 generation
activity of S2 was found to be about four times higher than that of pure Zn0.5Cd0.5S
(5.0 mmol h 1g 1) and about 240 times higher than that of CdS/1wt%Ni2P. The enhanced H2
generation activity of S2 has been attributed to efficient spatial separation of photogenerated
charge carriers and the presence of highly reactive Ni2P sites on the surface of
Zn0.5Cd0.5S microspheres. A possible mechanism for the enhanced photocatalytic H2 generation
activity of Zn0.5Cd0.5S/1wt%Ni2P (S2) has been proposed and is further supported by
photoluminescence and photocurrent measurements. Furthermore, the catalyst, S2 can be
recycled for several cycles without significant loss of catalytic activity and photostability.
Remarkably, the H2 generation activity of S2 was found to be even higher than the reported
examples of ZnxCd1-xS doped with noble metal cocatalysts. Hence, the present study
highlights the importance of Zn0.5Cd0.5S/Ni2P heterostructures based on non-noble metal
co-catalyst for efficient visible-light-driven H2 production from water splitting.
