A mesoporous WN co-doped titania nanomaterial with enhanced photocatalytic aqueous nitrate removal activity under visible light

This manuscript deals with the increased and selective nitrate reduction under visible light over a
WN co-doped titania photocatalyst. A series of WN co-doped titania nanomaterials were
synthesized with varying tungsten content and were characterized by TEM, XRD, UV-vis and
nitrogen adsorption–desorption studies. Tungsten doped materials are found to be noodle shaped
and mesoporous with a stable anatase phase after 500 1C calcination. Peak shifting in the XRD
pattern indicates the tungsten doping in the crystal lattice. Visible light absorption increases with
the increasing tungsten amount. Among the studied hole scavengers, formic acid was found to be
the best for nitrate reduction with more than 94% nitrogen gas selectivity. The amount of hole
scavenger also controls the reaction efficiency and product selectivity. Both nitrate reduction and
nitrogen gas selectivity increases with WN co-doping in comparison to only N doped titania.
High nitrate reduction with formic acid is attributed to the formation of CO2•– species having
high reduction potential. The material with 2% tungsten shows the highest surface area and the
best photocatalytic activity under visible light. Presence of anion like chloride increases the nitrate
photoreduction. Overall high nitrate reduction can be attributed to the synergistic effect of
tungsten and nitrogen co-doping, optimum surface hydroxyl group, mesoporosity and appreciable
visible light absorption of the materials.