Why is hydrogen gas used to reduce molybdenum oxide to metal?

Hydrogen gas is used to reduce molybdenum oxide to metal because it acts as an effective reducing agent, facilitating the removal of oxygen from the compound to produce pure molybdenum powder.12

In the industrial processing of molybdenum, chemically pure molybdic oxide or ammonium molybdate is subjected to a hydrogen reduction process. This is typically carried out in electrically heated tubes or muffle furnaces where hydrogen gas is introduced as a countercurrent against the feed. The reduction process is often performed in two stages: first, the oxide is reduced to a dioxide, and subsequently, it is reduced to metallic molybdenum powder. This method is essential for producing high-purity molybdenum, which can then be converted into massive metal through powder-metallurgy or arc-casting processes.13