In this paper, we give an overview of recent advances in the production of formic acid, as a hydrogen carrier, from CO2 and water by using the earth-abundant metal of Fe as the reductant under hydrothermal conditions, which mainly includes: 1) hydrogen production from water with Fe; 2) reduction of HCO3 to formic acid in the presence and absence of catalysts; 3) proposed reaction mechanisms. The novel options under this study are mainly the use of water as a hydrogen source with metal Fe as a reductant, and the formed FexOy as an auto-catalyst. Such a process possesses several benefits: (i) water acts not only as a hydrogen source but also as an environmentally benign solvent; (ii) there are no hydrogen requirements, including pumps or storage, because hydrogen is derived from water and reacts with CO2 in situ; (iii) no exotic catalysts or harsh reagents are used; and (iv) the method is simple and highly efficient. This technology can provide a one-step, sustainable and highly efficient way to reduce CO2 into formic acid using the hydrogen directly from water. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.