Hydrogen oxidation and reduction are fast reactions in polymer-electrolyte cells with modest amounts of noble metal catalyst.  Hydrogen can be pumped and compressed in a cell that oxidizes hydrogen at the anode at low pressure and reduces protons at high pressure at the cathode.  A typical hydrogen cell resembles a polymer-electrolyte fuel cell or electrolyzer with gas-diffusion electrodes containing platinum or a platinum alloy catalyst surrounding a polymer-electrolyte membrane like Nafion.  Hydrogen pumps can be more efficient and durable than mechanical compressors. 

Conventional polymer-electrolyte membranes like Nafion need to be moist in order to have high ionic conductivity.  This water is a nuisance in most applications; however one exception is a refrigeration cycle.  The thermodynamics of a refrigeration cycle with water as the working fluid driven by an electrochemical hydrogen pump is studied in this work.  In particular, an expression for the work done by the reactor is derived that includes terms associated with the partial pressure changes of hydrogen and water and irreversible losses.

The coefficient-of-performance (COP) of the hydrogen-pump system approaches the Carnot limit when the mole fraction of hydrogen entering the reactor is small (< 0.01).  Unfortunately, the amount of water crossing the membrane under these conditions far exceeds what can be supplied by osmotic drag.  The calculated COP at a hydrogen mole fraction of 0.1 is approximately half of the Carnot limit, a promising result, when the hot and cold reservoirs are at 40^oC and 20^oC.  Unfortunately, replacing a mechanical compressor with a hydrogen pump does not address the main issue with using water as refrigerant which is low total gas pressure.  Water has low vapor pressures at typical hot and cold reservoir temperatures.  Therefore, the electrochemical reactor would need to operate under vacuum and be designed to simultaneously provide low pressure drop and high mass transport rates.