CO production is now mature and cost-effective via two routes: efficient CO2 electro-reduction and CO separation from waste gas in industrial steel manufacturing. We reasoned that upgrading CO to a more valuable product was a topic that merited renewed focus. N-propanol, a liquid fuel suitable for engine fuel usage, has been detected in prior CO2/CO electro-reduction studies. Its high market value, including that measured per unit of energy, motivated our effort to increase the selectivity and activity of n-propanol electro-production.
We were curious if Cu adparticles possessing a high density of under-coordinated atoms could both concentrate CO coverage and enhance the stability of *C2 intermediates, promoting n-propanol generation. To assess this strategy we carried out density functional theory (DFT) calculations in which we explored adding under-coordinated Cu atoms on various Cu surfaces. We found that Cu adparticles not only enhance CO adsorption, but also diversify the CO adsorption sites, boosting CO-CO dimerization for multi-carbon production. The Cu adparticles also stabilized the surface *C2 intermediates, which is promising for n-propanol formation by intermolecular coupling with another adsorbed *CO.
We sought to trigger experimentally the growth of Cu adparticles immobilized on a Cu backbone. Real-time operando synchrotron hard X-ray absorption spectroscopy (hXAS) showed that in-situ synthesis of Cu catalysts mediated by intense CO chemisorption could lead to the growth of Cu adparticles. The metallic nature of active electrocatalysts was confirmed by both Operando hXAS and in-situ soft XAS.
Using the new catalyst we achieved a remarkable n-propanol selectivity of 23% with a high n-propanol formation current density of 11 mA cm-2. A higher n-propanol partial current density of 46 mA cm-2 was achieved with 11% n-propanol selectivity. We also investigated the correlation between structure and n-propanol generation efficiency. We found that preferential n-propanol production from adparticles was due to a higher population of low-coordinated surface sites, compared to nanobump and nanoparticle controls. This work exemplifies a C3 chemical fuel electrosynthesis from CO reduction using an adparticle approach, which not only provides an avenue towards high-chain carbon products formation, but may also be applied to improve the performance of other metal catalysts.
A detailed story can be found in Nature Communications.
This blog story is written by Jun Li, Edward H. Sargent and David Sinton.