Stainless Steel Ball Milling for Hydrogen Generation and its Application for Reduction

Abstract

Hydrogen (H₂) is an environmentally friendly energy source that produces only water through combustion and is a useful reducing agent in organic chemistry. However, according to the law, it needs to be strictly stored, transported, and managed in pressure vessels. Although H₂ is mainly produced industrially by the steam reforming of methane (CH₄), this is not environmentally friendly owing to the emissions of carbon dioxide (CO₂) as well as the energy input from the endothermic reaction. Herein, hydrogen generation is achieved from water (H₂O and D₂O), alkane, and diethyl ether (Et₂O) without CO₂ emissions through the mechanochemical collision of stainless-steel balls using a planetary ball mill machine. Furthermore, in situ generated H₂ can be directly utilized as a reductant for various reducible functionalities, such as alkynes, alkenes, ketones, nitro groups, and aromatic halides. In addition, D₂ derived from D₂O promotes a reductive deuteration to provide the corresponding deuterated products. When using Et₂O as a hydrogen source, a reduction of arene can be achieved. In this paper, the hydrogen generation from water, alkanes, and Et₂O, subsequent hydrogenation, and the role of stainless-steel balls are summarized.