Ni-Ti layered double hydroxides, as nickel hydroxide, can be employed as oxidation catalysts, active materials for accumulators and supercapacitors, electrochromic materials etc. As a rule, the catalyst’s activity depends on synthesis method and synthesis conditions.
Samples of Ni-Ti LDH were prepared using titration method by adding NaOH solution to acidified solution of nickel and titanium salts at different temperatures. First sample was prepared at room temperature. Second sample was prepared at 60 oC, and after precipitation was subjected to hydrothermal treatment at same temperature during 17 h.
The catalytic activity was evaluated for formaldehyde electrooxidation reaction by recording cyclic voltamperograms. The electrodes were prepared by pasting active mass, composted of hydroxide powder, graphite and PTFE, on platinum substrate. The platinum substrate was chosen because in basic media platinum doesn’t demonstrate electrocatalytic activity towards formaldehyde electrooxidation in potential window of nickel hydroxide cycling. The cycling was conducted in 1M KOH and 1M KOH with addition of formaldehyde in potential window of 301-751 mV (vs NHE).
The results of cycling have showed, that without formaldehyde in electrolyte, the cyclic curves of samples demonstrate form characteristic for α-Ni(OH)2. The α-structure was confirmed by means of XRD, TGA and DSC. With formaldehyde present in electrolyte, the anodic current corresponding to oxidation of nickel increased significantly, while cathodic current corresponding to nickel reduction was almost absent. This indicated that electrooxidation of formaldehyde on Ni-Ti LDH is a catalytic process, with Ni3+ atoms mediating the process.
During cycling in 1M KOH with addition of formaldehyde, the current values for sample prepared at room temperature were lower only by ~5%, at same potential values. This indicates that during synthesis of Ni-Ti LDH as catalyst for formaldehyde oxidation, the employment of high synthesis temperatures is not advisable.