A sol-immobilization method is used to synthesize a series of highly active and stable Au
x
Pd
1−
x
/TiO
2
catalysts (where
x
= 0, 0.13, 0.25, 0.5, 0.75, 0.87 and 1) for wastewater remediation. The catalytic performance of the materials was evaluated for the catalytic reduction of 4-nitrophenol, a model wastewater contaminant, using NaBH
4
as the reducing agent under mild reaction conditions. Reaction parameters such as substrate/metal and substrate/reducing agent molar ratios, reaction temperature and stirring rate were investigated. Structure-activity correlations were studied using a number of complementary techniques including X-ray powder diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. The sol-immobilization route provides very small Au–Pd alloyed nanoparticles, with the highest catalytic performance shown by the Au
0.5
Pd
0.5
/TiO
2
catalyst.
This article is part of a discussion meeting issue ‘Science to enable the circular economy’.
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