Synthesis of NaBH4 based on a solid-state reaction under Ar atmosphere

Sodium borohydride, NaBH4, was successfully synthesized via solid-state reaction under Ar instead of H2 atmosphere. A 4NaH–NaBO2–2SiO2 ternary mixture was first ball-milled and pressed into pellet, and then calcined under Ar atmosphere at 480 °C for 5 h. NaBH4 was obtained in 32% yield when the pressing pressure was up to 30 MPa. The influence of the pressing pressure on the solid-state reaction was studied; a plausible reaction pathway and the role of the added SiO2 were discussed.