Toward benchmarking theoretical computations of elementary rate constants on catalytic surfaces: formate decomposition on Au and Cu

With the emergence of methods for computing rate constants for elementary reaction steps of catalytic reactions, benchmarking their accuracy becomes important. The unimolecular dehydrogenation of adsorbed formate on metal surfaces...

Cationic poly-L-amino acid-enhanced selective hydrogen production based on formate decomposition with platinum nanoparticles dispersed by polyvinylpyrrolidone

Formate is attracting attention as a hydrogen carrier because of its low toxicity and easy handling in aqueous solution. In order to utilize formic acid as a hydrogen carrier, a...

On-line analysis and in situ pH monitoring of mixed acid fermentation by Escherichia coli using combined FTIR and Raman techniques

We introduce an experimental setup allowing continuous monitoring of bacterial fermentation processes by simultaneous optical density (OD) measurements, long-path FTIR headspace monitoring of CO2, acetaldehyde and ethanol, and liquid Raman spectroscopy of acetate, formate, and phosphate anions, without sampling. We discuss which spectral features are best suited for detection, and how to obtain partial pressures and concentrations by integrations and least squares fitting of spectral features. Noise equivalent detection limits are about 2.6 mM for acetate and 3.6 mM for formate at 5 min integration time, improving to 0.75 mM for acetate and 1.0 mM for formate at 1 h integration. The analytical range extends to at least 1 M with a standard deviation of percentage error of about 8%. The measurement of the anions of the phosphate buffer allows the spectroscopic, in situ determination of the pH of the bacterial suspension via a modified Henderson-Hasselbalch equation in the 6–8 pH range with an accuracy better than 0.1. The 4 m White cell FTIR measurements provide noise equivalent detection limits of 0.21 μbar for acetaldehyde and 0.26 μbar for ethanol in the gas phase, corresponding to 3.2 μM acetaldehyde and 22 μM ethanol in solution, using Henry’s law. The analytical dynamic range exceeds 1 mbar ethanol corresponding to 85 mM in solution. As an application example, the mixed acid fermentation of Escherichia coli is studied. The production of CO2, ethanol, acetaldehyde, acids such as formate and acetate, and the changes in pH are discussed in the context of the mixed acid fermentation pathways. Formate decomposition into CO2 and H2 is found to be governed by a zeroth-order kinetic rate law, showing that adding exogenous formate to a bioreactor with E. coli is expected to have no beneficial effect on the rate of formate decomposition and biohydrogen production.

Catalytic mechanism for selective hydrogen production based on formate decomposition with polyvinylpyrrolidone-dispersed platinum nanoparticles

To clarify the HCOOH decomposition into H2 and CO2 mechanism with Pt-PVP, a pH or HCOO− concentration dependence of H2 production rate with Pt-PVP, IR spectra was studied and the possible catalytic mechanism of H2 production was proposed.

Enhancement of catalytic activity for selective hydrogen production from formate with homogeneously poly(vinylpyrrolidone)/cationic poly(l-lysine) dispersed platinum nanoparticles

By using Pt nanoparticles dispersed by polyvinylpyrrolidone and cationic biopolymer, poly(l-lysine) (Pt–PVP/PLL), the highly selective H2 production based on formate decomposition was accomplished compared with that of Pt–PVP.

Palladium Supported on Porous Chitosan–Graphene Oxide Aerogels as Highly Efficient Catalysts for Hydrogen Generation from Formate

Adsorption of Pd(NH3)42+ in preformed chitosan–graphene oxide (CS-GO) beads and their subsequent reduction with NaBH4 afford well-dispersed, high dispersion (~21%) of uniformly sized Pd nanoparticles (~1.7 nm). The resulting Pd/CS-GO exhibits interesting catalytic activity for hydrogen generation by ammonium formate decomposition. The optimal GO proportion of 7 wt% allows reaching, at 60 °C, a turnover frequency above 2200 h−1—being outstanding among the highest values reported for this process to date. Interestingly, no formation of CO or CH4 was detected. The catalyst did not leach, although it underwent gradual deactivation, probably caused by the increase in the Pd average size that became over 3 nm after three uses. Our results are relevant in the context of efficient on-board hydrogen generation from liquid organic hydrogen carriers in transportation.

Synthesis of Ni nanoparticles with controlled pyrophoricity and mean size

This study establishes that nickel formate decomposition in an argon flow at 209°C and subsequent processing of the obtained nanopowder in a hydrogen flow within a specified time interval, make it possible to control the pyrophoricity and average size of Ni particles.