PNNL

Abstract

We present two processes that enable the use of formic acid (HCOOH) as a liquid hydrogen carrier to store renewably-generated electrical energy and then release it to generate electrical power cleanly for backup or emergency applications. First, we show that simultaneously oxidizing an organic solute (typically a waste stream) can assist the electrochemical synthesis of formic acid by lowering the cell potential—we call that coupling “Anode Boosting”. The electrolyzer comprises a hybrid 3-chamber PEM stack that reduces CO2 via a gas-diffusion cathode boosted by the oxidation of aqueous methanol. However, the extent of the boosting needs to be optimized across the whole operation of the cell. Next, we present results from an intensified catalytic reactor for decomposing the formic acid back into H2 and CO2 so that the H2 can be used in a fuel cell. The reactor combines three operations: vaporization of the formic acid, its decomposition, and separation of the product stream. Their close coupling affords energy savings and a compact design that could be mounted on a mobile skid. We will discuss the electrode catalyst that facilitates the first process and the thermally activated catalyst that enables the second process.