Visible‐Light Driven Ni‐Incorporated CdS Photocatalytic Activities for Azo‐Bond Cleavages with Hydrogenation Reaction

Ni‐incorporated CdS (Ni‐CdS) photocatalysts with different amounts of Ni dopant have been synthesized, characterized, and examined toward azo‐bond cleavages in visible‐light illuminated conditions. The optimum performance was achieved with a relatively low amount of Ni dopant (2 % atomic mass). The azo bonds of azobenzene (AB) and methyl orange (MO) compounds were hydrogenated with the in‐situ generated hydrogen on Ni‐CdS catalyst surfaces. The hydrogen evolution reaction was proved and measured with GC measurement during the photocatalytic session with an incandescent halogen lamp. Furthermore, the experimental data of UV‐vis spectra analyses suggested the formation of aniline or sodium sulfanilate and p‐aminodimethylaniline with the emerged peaks at ∼240 nm, indicating azo‐bond has been cleaved in AB or MO compounds, respectively. The catalytic performances of 2 % Ni‐CdS are also supported with electrical and photoresponse analyses. To demonstrate the possibility of industrial application, Ni‐CdS catalyst stability is also tested for several runs in reusability experiments and examined with cyclic voltammetry for 100 cycles without any significant degradation. The cleavage mechanisms of azo bonds in AB and MO compounds were discussed and proposed in this work. The catalytic performances of 2 % Ni‐CdS exhibited excellent electrical and photoresponse properties. It has been demonstrated the possibility of industrial application with Ni‐CdS catalyst. The catalyst can achieve a hydrogen evolution rate of ∼710 μmol/h and the evolved hydrogen can be used for hydrogenation reaction to cleave azo‐bonds in MO and azobenzene. Ni‐CdS catalyst‘s reusability has been shown for several runs and is further examined with cyclic voltammetry for 100 cycles without any significant degradation.