Increased hydrogen partial pressure suppresses and reverses hydrogen evolution during Pd catalysed electrolysis of CO₂

Abstract

<p>Control over selectivity towards HCOO⁻ rather than H₂ is acquired by using elevated pressure of hydrogen during CO₂ electrolysis.</p>

Mechanism and Micro Kinetic Model for Electroreduction of CO2 on Pd/C: The Role of Different Palladium Hydride Phases

“…A specialized electrochemical setup was designed which facilitates experiments at elevated pressure with an incorporated, stable Ag/AgCl reference electrode. The electrochemical cell, setup, experimental procedure, and electrode preparation method are described in detail elsewhere . In short, experiments were performed in a sandwich-type electrochemical cell, divided by a cation exchange membrane.…”

“…Interestingly, in previous work, we observed experimentally that hydrogen formation could be prevented by increasing the partial hydrogen pressure, an effect that occurred well below the equilibrium pressure of H 2 (reaction ) as calculated via Nernst’s law. We did not observe any significant changes in the rate to formate and consequently observed decreasing current as a function of the partial pressure of hydrogen.…”

Selective electrochemical reduction of CO2 to formic acid in a gas phase reactor with by-product recirculation

“…Recently, Kersten et al experimentally explored the use of increasing the hydrogen partial pressure to suppress additional hydrogen formation on a Pd electrocatalyst in a liquid electrolyte. 30 A pressurized reactor vessel was used, with controlled amounts of added hydrogen gas. Raising the partial pressure of hydrogen led to a decrease of hydrogen production, while the formate production rate was maintained.…”

“…Raising the partial pressure of hydrogen led to a decrease of hydrogen production, while the formate production rate was maintained. 30 Although this approach is promising, it requires an external input of hydrogen gas. If not precisely controlled, this could result in side reactions.…”

“…Additionally, a high CO2 concentration leads to a more acidic aqueous environment, likely increasing the HER. 30 Lowering the CO2 partial pressure is thus not necessarily detrimental to the CO2RR and could even be beneficial.…”