Which of the following elements is NOT typically used as a catalyst inside a three-way catalytic converter?

In the context of a three-way catalytic converter, a catalyst is a substance that speeds up chemical reactions without being consumed in the process. The primary function of this converter is to reduce harmful emissions from the engine's exhaust by facilitating three key reactions: converting carbon monoxide (CO) into carbon dioxide (CO2), converting hydrocarbons (HC) into carbon dioxide and water (H2O), and oxidizing nitrogen oxides (NOx) into nitrogen (N2) and oxygen (O2).

Palladium, platinum, and rhodium are precious metals commonly employed as catalysts in three-way catalytic converters. Palladium and platinum are effective for oxidizing CO and HC, while rhodium is crucial for the reduction of NOx. These metals are chosen for their ability to endure high temperatures and their catalytic properties that lead to the effective transformation of harmful gases into less harmful substances.

Titanium, on the other hand, is not typically used as a catalyst in three-way catalytic converters. While it has some catalytic properties, it is not effective in the specific reactions that the converter is designed to promote. Its use in catalytic converters is limited, which is why it stands out as not being a standard catalyst material in these applications. Thus, the answer is