Development of bifunctional molybdenum-substituted NiO nanocatalyst for the maximization of photocatalysis and gas sensor activities

Bifunctional NiO nanocatalyst with Mo⁶⁺ substitution was prepared through a simple precipitation technique, and the specimens were well characterized by p-XRD, SEM, HR-TEM, UV–Vis DRS, PL, and HR-XPS techniques. The obtained Mo⁶⁺-substituted NiO revealed enhanced photocatalytic activity for the degradation of MO aqueous solution and 90.61% of the MO dye was photodegraded using 1.5% Mo⁶⁺-doped NiO within 180 min under UV–Vis light illumination, which is higher than that of pristine and 0.5%, 1% and 2% of the Mo⁶⁺-substituted NiO nanocatalyst. The substituent Mo⁶⁺ played a strategic role, which narrowed the energy band gap and suppressed the photoinduced electron–hole recombination by forming an inner energy state. Scavenging experiments revealed that hydroxyl radicals were the predominant active radicals, and recycling experiments revealed that the catalyst was highly stable. Furthermore, the findings of gas sensing experiments demonstrated that the substitution of Mo⁶⁺ on the NiO crystal structure considerably improved the triethylamine (TEA) sensing property of NiO. The mechanism of photocatalytic degradation and gas detection was demonstrated.