posted on 2021-11-15, 19:37authored byJavad Safaei, Seyed Mostafa Hosseinpour Mashkani, Hao Tian, Caichao Ye, Pan Xiong, Guoxiu Wang
Capacitive
deionization (CDI) is a promising and energy-efficient
technology for desalination. The development of high-performance capacitive
electrodes is essential for enhancing the CDI properties for practical
applications. Here, a 2D heterostructure was rationally designed and
synthesized by face-to-face restacking of NbOPO4 nanosheets
and reduced graphene oxide (rGO) via an electrostatic self-assembly
process. The as-prepared 2D NbOPO4/rGO heterostructure
achieved an excellent ion storage capacity, electronic conductivity,
and unimpeded ion kinetics. When applied as electrodes for CDI, the
2D NbOPO4/rGO heterostructure delivered a high specific
capacitance of 258.3 F g–1 and an electrosorption
capacity of 73 mg g–1 for NaCl solution of 10 000
mg L–1 at an applied voltage of 1.2 V, which is
more than five times larger than that of activated carbon. The heterostructure
electrode also showed high desalination stability for up to 50 adsorption/desorption
cycles. The high CDI performance is attributed to the strong 2D/2D
coupling between NbOPO4 nanosheets and rGO. The strong
2D/2D coupling reduced the charge transfer resistance, affirmed via
the electrochemical impedance spectroscopy technique, attesting to
the enhanced charge transportation across the heterointerface. The
robust 2D/2D coupling was affirmed via the uniform and identical Raman
shifts at various random regions, and larger XPS binding energy shifts
for the self-assembled NbOPO4/rGO heterostructure. This
work demonstrated the potential of self-assembled nanoheterostructures
for water desalination via capacitive deionization.