Page 51 - Annual Report_21-22

Chemically coupled Hematite-rGO electrocatalyst for nitrogen reduction to ammonia

The chemically coupled hematite with rGO was
successfully synthesized, as confirmed by the XRD and
Raman analysis. The FTIR analysis was further confirmed,
by the presence peak at 568 cm corresponding to the Fe-
-1
O-C bond. The chemically coupled hematite/rGO shows
enhanced activity for the nitrogen reduction reaction
(NRR) than that of bare α-Fe O and GO, attributed to
3
2
the improved e- transport across the interface and higher
degree of N activation for NRR catalysis, Figure 3. These
2
findings serve as an example to design an inexpensive but
efficient catalyst by chemically coupling for the NRR.

Fig. NH3 yield rate of hematite/rGO
Ultrafast synthesis of Ti3SiC2 MAX phase by reactive Flash sintering for production of 2-D
material Ti3C2TX MXene

MXenes, a new class of two-dimensional transition metal conventionally synthesized Ti SiC MAX phase. The novelty
3
2
carbides, nitrides and carbonitrides (MXenes) have out- of our research is its ability to synthesize different MAX
performed other 2D nanomaterials and rapidly position- phases with the desired composition in any atmosphere
ing in numerous promising applications due to their ex- (Vacuum, inert or air) in bulk using the ultrafast Flash sin-
tra-ordinary properties. MXenes, provide very attractive tering technique. The use of the flash sintering technique
building blocks for a very large variety of applications, such presented here for the synthesis of the MAX phase is an
as energy storage, including super capacitors, lithium-ion innovative and scalable approach capable of producing
batteries, oxygen evolution reaction, heavy metal adsorp- MAX phases in large quantities in a short time. Thus, it
tion, water purification, electrocatalysis for H generation, could be a breakthrough for the rapid synthesis of a wide
2
medicine, and transparent coatings etc. Production of MX- range of MAX phases on an industrial scale
ene is still at a very early stage. One of the limiting factors
for large-scale and low-cost manufacturing of MXenes is
the cost and limited availability of MAX phases. Howev-
er, making good-quality MXene requires not just “a MAX”,
but a MAX phase with appropriate properties optimized
for MXene synthesis. The existing conventional methods
for the synthesis of MAX phases are expensive, complex,
time and power consuming. Here, we have developed an
ultrafast route with a cost-effective, consolidated flash
sintering technology for the synthesis of the Ti SiC MAX
2
3
phase which is feasible in the air as well as in a vacuum.
Here, a relatively low voltage (35-42 V/cm) was applied
using a DC power source across a compact Ti/Si/C mix-
ture sandwiched between two graphite electrodes, prior
to ignition at a constant external heating temperature of
300 C. Strong light emission was observed confirming the Figure: Field emission scanning electron microscope
o
flashing event for just 10-15 seconds with a quick rise in (FESEM) image of (a) flash synthesized Ti SiC MAX phase
2
3
current flow and temperature with a heating rate of about showing typical compact layered structure, (b) clearly
open layered structure of Ti C T MXene after etching in
450 C/sec within the sample. Two-dimensional Ti C T HF/H O , (c) well-defined accordion like morphology of
o
3 2 X
3 2 X
MXene nanosheets were successfully synthesized from multi-layered Ti C T MXene stack at higher magnification,
2
2
3 2 X
the flash synthesized Ti SiC MAX phase by oxidant-assist- (d) more expanded and well separated Ti C T
3
2
3 2 X
ed HF etching. The MXene thus obtained exhibited com- MXene nanosheets after de-lamination using TBAOH.
parable properties to that previously reported from the
ANNUAL REPORT 2021-22 49