posted on 2024-01-03, 18:04authored bySudeshna Das Chakraborty, Uttam Kumar, Pallab Bhattacharya, Trilochan Mishra
A wide
solar light absorption window and its utilization, long-term
stability, and improved interfacial charge transfer are the keys to
scalable and superior solar photocatalytic performance. Based on this
objective, a noble metal-free composite photocatalyst is developed
with conducting MXene (Ti3C2) and semiconducting
cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and
ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface
of Ti3C2 during hydrothermal treatment, thus
creating a third semiconducting site with enough oxygen vacancy. The
final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from
300 to 2000 nm, covering the visible to near-infrared (NIR) range
of the solar spectrum. Photocatalytic H2 generation activity
is found to be 12.23 and 16.26 mmol g–1 h–1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively,
with good repeatability under visible–NIR light using lactic
acid as the hole scavenger. A clear increase of efficiency by 1.53
mmol g–1 h–1 in the tertiary composite
due to NIR light absorption supports the intrinsic upconversion of
electrons, which will open a new prospective of solar light utilization.
Decreased charge-transfer resistance from the EIS plot and a decrease
in PL intensity established the improved interfacial charge separation
in the tertiary composite. Compared to pure CdS, H2 generation
efficiency is 29.6 times higher on the noble metal-free tertiary composite
with an apparent quantum efficiency of 12.34%. Synergistic effect
of defect-enriched TiOy formation, creation
of proper dual p–n junction on a Ti3C2 sheet as supported by the Mott–Schottky plot, significant
NIR light absorption, increased electron mobility, and charge transfer
on the conductive Ti3C2 layer facilitate the
drastically increased hydrogen evolution rate even after several cycles
of repetition. Expectantly, the 2D MXene-based heterostructure with
defect-enriched dual p–n junctions of desired interface engineering
will facilitate scalable photocatalytic water splitting over a broad
range of the solar spectrum.