Hydrogen Production from Formic Acid Attained by Bimetallic Heterogeneous PdAg Catalytic Systems

Abstract

The production of H 2 from the so-called Liquid Organic Hydrogen Carriers (LOHC) has recently received great focus as an auspicious option to conventional hydrogen storage technologies. Among them, formic acid, the simplest carboxylic acid, has recently emerged as one of the most promising candidates. Catalysts based on Pd nanoparticles are the most fruitfully investigated, and, more specifically, excellent results have been achieved with bimetallic PdAg-based catalytic systems. The enhancement displayed by PdAg catalysts as compared to the monometallic counterpart is ascribed to several effects, such as the formation of electron-rich Pd species or the increased resistance against CO-poisoning. Aside from the features of the metal active phases, the properties of the selected support also play an important role in determining the final catalytic performance. Among them, the use of carbon materials has resulted in great interest by virtue of their outstanding properties and versatility. In the present review, some of the most representative investigations dealing with the design of high-performance PdAg bimetallic heterogeneous catalysts are summarised, paying attention to the impact of the features of the support in the final ability of the catalysts towards the production of H 2 from formic acid.Energies 2019, 12, 4027 2 of 27 fact, it is challenging not only for developed countries in which the living standard requires large energy supplies, but also for those developing countries that experience a high population growth.Among greenhouse gases, carbon dioxide (CO 2 ) is considered the most important because, even though its global warming potential (GWP) is much lower than that of other gases, the emissions of CO 2 are far more abundant. GWP parameter was developed to compare the global warming impacts of different gases and it is a measure of how much energy the emissions of 1 ton of a gas will absorb over a given period, relative to the emissions of 1 ton of CO 2 , which is used as the reference. Then, CO 2 has a GWP of 1 regardless of the time used, while GWP is 28-36 and 265-298 times that of CO 2 for methane (CH 4 ) and nitrous oxide (N 2 O), respectively [1]. Such considerations, that are nowadays central scientific and social concerns, have a long historical background within the research community. Arrhenius was among the first to hypothesise about the impact of CO 2 on the Earth's climate [2], but his hypothesis was overlooked until the 1950s [3]. Now, after more than half a century, there is not yet a chemical process able to efficiently clean the growing volumes of CO 2 in the atmosphere. Some interesting actions taken so far are related to the production of hydrocarbon fuels by recycling H 2 O and CO 2 with renewable energy sources or the CO 2 capture and sequestration (CCS) technology [4][5][6][7].In such energy and environmental context, the search for alternative carbon emission-free energy sources is required to avoid further disastrous consequences. Hydrogen (H 2 ), a carbon-free fuel, is consi...

Decomposition of Additive-Free Formic Acid Using a Pd/C Catalyst in Flow: Experimental and CFD Modelling Studies

“…The main reason for deactivation of the Pd/C catalyst is poisoning of the catalyst [35]. The majority of research groups have proposed that the CO is the poisoning molecule [36][37][38][39]. CO can adsorb stronger on Pd than CO 2 and H 2 , [40] and it has been shown by using Attenuated Total Reflection Infrared Spectroscopy (ATR-IR).…”

H2 Production from Formic Acid Using Highly Stable Carbon-Supported Pd-Based Catalysts Derived from Soft-Biomass Residues: Effect of Heat Treatment and Functionalization of the Carbon Support

“…The production of hydrogen from FA proceeds via a dehydrogenation reaction (HCOOH ↔ H 2 + CO 2 ) that can be promoted by both homogeneous [ 12 , 13 ] and heterogeneous [ 14 , 15 , 16 ] catalysts, the latter being the preferred choice because of advantages associated with their use. The heterogeneous catalysts used in this reaction are frequently based on Pd nanoparticles supported on materials of diverse composition [ 6 , 17 , 18 , 19 , 20 , 21 , 22 ], with carbon materials being some of the most common supports [ 7 , 23 , 24 ].…”

MWCNT-Supported PVP-Capped Pd Nanoparticles as Efficient Catalysts for the Dehydrogenation of Formic Acid

“…Formic acid, the simplest carboxylic acid (HCOOH, FA), has recently received great interest as a hydrogen carrier molecule (Enthaler et al, 2010;Grasemann and Laurenczy, 2012;Navlani-García et al, 2019a;Valentini et al, 2019). The increasing literature reporting on that topic is particularly notorious in the last decade, when numerous approaches to design efficient catalysts to boost the dehydrogenation of FA have been considered.…”