Ultrafast detection of ammonia at room temperature and subsequent electrochemical water splitting via the ionic liquid templated nano nickel oxide

Abstract

In this work, biopolymers like chitosan and Bovine Serum Albumin (BSA) templated and ionic liquid (IL)-driven synthesis of crystalline NiO nanoparticles for ultrafast room temperature detection of ammonia together with its semi-empirical mechanistic details are reported. The XRD results have revealed the crystalline nature of synthesized NiO nanoparticles; the contact angle measurements for the adhesive nature of the NiO nanoparticles have been carried out and the films have been subjected to gas sensing studies by chemo-resistive method. The as-prepared BSA templated ionic liquid driven NiO based thin film sensor displays an ultrafast response for the room temperature detection of ammonia with an excellent response and recovery times of 38 and 13 s, respectively, towards a lower detection limit up to 1 ppm. The ultrafast sensing mechanism of the ammonia has been deduced with the aid of X-ray Photoelectron Spectroscopy (XPS) analysis. Furthermore, as-synthesized BSA/BSA-IL templated NiO electrodes have displayed excellent electrocatalytic water oxidation in alkaline media, with a collective water-splitting stable current density of 10 mA∙cm−2. We have observed the HOMO-LUMO gap and the Valence Band/Conduction Band (VB/CB) position from the Bredas method calculations which clarifies the highest aptitude of NiO prepared with BSA-IL template for superfast ammonia gas sensing as the CB energy is significantly lower than that of NiO synthesized via the BSA template. The dual approach of multifarious applications for the ultrafast ammonia sensing and the corresponding electrochemical water oxidation through the bio-inspired NiO-nanoparticles is in fact one of the novel applications being cited in this paper. The results highlight the grave implications of as-synthesized NiO-nanoparticles as a brilliant cost-effective gas sensor and as an effective alternative electrode for sustainable energy harvesting.