Selective catalytic hydrogenation of nitrobenzene (Ph-NO₂) to high value-added azoxy-, azo- and aminobenzene compounds are considerably important in the organic synthesis industry.

Compared with traditional thermocatalytic processes, the electrocatalysis technique has aroused great research attention, owing to its high hydrogenation efficiency, ambient operating conditions. Unfortunately, the relevant selective hydrogenation mechanisms are unclear in the reported works.

Recently, researchers led by Prof. ZHANG Haimin from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS) reported the ultrafine Cu_xPt_y alloying nanoparticles anchored on carbon black (Cu_xPt_y/C) to achieve potential regulation of electrocatalytic hydrogenation of Ph-NO₂ and proposed a new hydrogenation mechanism. The result was published on Applied Catalysis B: Environmental.

The researchers prepared a series of Cu_xPt_y alloying nanoparticles and they found that the Cu₃Pt/C can afford almost 100% conversion of Ph-NO₂ into azoxybenzene with ~99% selectivity at 0.3 V (vs. RHE) and aminobenzene with ~99% selectivity at -0.3 V (vs. RHE) in 1.0 M potassium hydroxide, respectively.

Moreover, the Cu₃Pt/C was put into the large-scale electrocatalytic experiment, and the morphology, structure, and activity had no significant change after a long time electrocatalytic test.

Meanwhile, theoretical calculations provided a comprehensive understanding of the selective electrocatalytic hydrogenation mechanisms of Ph-NO₂ relative to electrolyte pH and applied potential.

This work was supported by the Natural Science Foundation of China, and the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences, China.

Theory and experiment combined to explore the selectivity of nitrobenzene electrocatalytic hydrogenation products under different potential and pH conditions (Image by JIN Meng)