Approximately 80% of all rhodium produced globally is used in automotive catalytic converters. Rhodium is uniquely effective at reducing nitrogen oxides (NOx) — one of the most harmful exhaust pollutants — by converting them into harmless nitrogen gas. Even tiny amounts of rhodium dramatically improve catalytic converter performance, which is why it is paired with platinum and palladium in three-way catalysts. As global emissions standards (Euro 6, China 6, US Tier 3) become increasingly strict, demand for rhodium has surged, driving its price to historic highs and making it the most expensive precious metal on Earth.

Rhodium's bright reflective finish, exceptional hardness, and resistance to tarnishing make it the premier choice for plating fine jewelry. White gold rings, earrings, and necklaces are typically electroplated with a thin layer of rhodium (0.75–1.0 microns) to enhance their whiteness, hardness, and resistance to scratches. Sterling silver is also rhodium-plated to prevent tarnishing. Rhodium plating is hypoallergenic, making it ideal for people with metal sensitivities. The plating typically lasts 1–2 years before requiring reapplication, depending on wear.

Rhodium catalysts are critical in numerous industrial chemical processes. Platinum-rhodium gauzes are used in the Ostwald process to produce nitric acid — a fundamental feedstock for fertilizers, explosives, and dyes. Rhodium catalysts also drive the Monsanto and Cativa processes for producing acetic acid, hydroformylation reactions to manufacture aldehydes and alcohols, and the synthesis of silicones used in everything from medical devices to industrial sealants. Despite high cost, rhodium's selectivity and stability make it irreplaceable in these high-value chemical industries.

Platinum-rhodium alloys are used to make bushings — perforated containers through which molten glass is drawn into fibers — in the production of fiberglass and specialty optical glass for LCD/OLED displays. These alloys can withstand temperatures above 1,500°C while resisting corrosion from molten glass. Rhodium is also used in thermocouples for high-temperature measurement (up to 1,800°C), in electrical contacts where reliability and corrosion resistance are critical, and in mirrors for searchlights, headlamps, and scientific instruments due to its superior reflectivity in the visible and infrared spectrum.