Electro-catalytic conversion of ethanol in solid electrolyte cells for distributed hydrogen generation

A Novel Chemical-Electrochemical Hydrogen Production from Coal Slurry by a Two-Step Process: Oxidation of Coal by Ferric Ions and Electroreduction of Hydrogen Ions

Hydrogen production from the electrolysis of coal slurry is a promising approach under the condition of low voltage (0.8-1.2 V) and medium temperature. However, the rate of hydrogen production is slugged by poor anode kinetics, under an electrochemical condition that results from the collision of the coal particles with the anode surface. This paper reports a novel process that consists of two steps: the oxidation of the coal slurry by ferric ions(III) in a hydrothermal reactor at a temperature of 120-160 °C and the electro-oxidation of ferric ions(II) in the electrochemical cell to produce hydrogen. This technique circumvents the technical issues experienced in the conventional coal slurry electrolysis process by adopting a two-step process consisting of solid-liquid reactions instead of solid-solid reactions. This indirect oxidation process produced a current density of 120 mA/cm² at room temperature and a voltage of 1 V, which is higher than the values reported in the conventional processes. An investigation of the oxidation mechanism was carried out via scanning electron microscopy, Fourier-transform infrared spectroscopy and elemental analysis. The results obtained showed that the oxidation of coal by ferric ions occurs from the surface to the inner parts of the coal particles in a stepwise manner. It was also revealed that the ferric ions in the media increased the active interfaces both of the coal particles and of the anode electrode. This explains the high hydrogen production rate obtained from this process. This novel discovery can pave the way for the commercialization of coal slurry electrolysis.

Green ammonia synthesis using CeO2/RuO2 nanolayers on vertical graphene catalyst via electrochemical route in alkaline electrolyte

The electrochemical synthesis of ammonia at ambient temperature and pressure has the potential to replace the conventional process for the production of ammonia. However, the low ammonia yield and poor long-term stability of catalysts for the synthesis of ammonia hinders the application of this technology. Herein, we endeavored to tackle this challenge by synthesizing 3-D vertical graphene (VG) on Ni foam via a one-step, low-temperature plasma process, which offered high conductivity and large surface area. Subsequently, the vertical graphene on Ni foam was loaded with nanolayers of ruthenium oxide (RuO₂, ∼2 nm) and cerium oxide (CeO₂, <20 nm) nanoparticles via magnetron sputtering. The incorporation of nanoparticle layers (RuO₂ and CeO₂/RuO₂) on VG significantly increased the NH₃ yield in KOH electrolyte. Finally, the performance and long-term stability of this composite material were successfully demonstrated by the addition of CeO₂/RuO₂ nanolayers on the VG electrocatalyst. The catalyst achieved an excellent performance with a high ammonia synthesis yield of 50.56 μg mg_{total cat.}^-1 h^-1 (1.11 × 10^-10 mol cm^-2 s^-1) during the performance evaluation period of 36 h. This observation was also verified by density functional theory calculation, where CeO₂ exhibited the best catalytic performance compared to RuO₂ and pristine graphene.

Engineering a solid-state metalloprotein hydrogen evolution catalyst

Hydrogen has the potential to play an important role in decarbonising our energy systems. Crucial to achieving this is the ability to produce clean sources of hydrogen using renewable energy sources. Currently platinum is commonly used as a hydrogen evolution catalyst, however, the scarcity and expense of platinum is driving the need to develop non-platinum-based catalysts. Here we report a protein-based hydrogen evolution catalyst based on a recombinant silk protein from honeybees and a metal macrocycle, cobalt protoporphyrin (CoPPIX). We enhanced the hydrogen evolution activity three fold compared to the unmodified silk protein by varying the coordinating ligands to the metal centre. Finally, to demonstrate the use of our biological catalyst, we built a proton exchange membrane (PEM) water electrolysis cell using CoPPIX-silk as the hydrogen evolution catalyst that is able to produce hydrogen with a 98% Faradaic efficiency. This represents an exciting advance towards allowing protein-based catalysts to be used in electrolysis cells.

Pt/C and Pt/SnOx/C Catalysts for Ethanol Electrooxidation: Rotating Disk Electrode Study

Pt/C and Pt/SnOx/C catalysts were synthesized using the polyol method. Their structure, morphology and chemical composition were studied using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer, transition electron microscope and X-ray photoelectron spectroscope. Electrochemical measurements were based on the results of rotating disk electrode (RDE) experiments applied to ethanol electrooxidation. The quick evaluation of catalyst activity, electrochemical behavior, and an average number of transferred electrons were made using the RDE technique. The usage of SnOx (through the carbon support modification) in a binary system together with Pt causes a significant increase of the catalyst activity in ethanol oxidation reaction and the utilization of ethanol.

Intermediate-temperature electrolysis of energy grass Miscanthus sinensis for sustainable hydrogen production

Biohydrogen produced from the electrolysis of biomass is promising because the onset voltages are less than 1.0 V and comparable to those of water and alcohol-water electrolysis. The present study focuses on Miscanthus sinensis as a model grass because of its abundance and ease of cultivation in Japan. The electrochemical performance and hydrogen formation properties of electrolysis cells using grass as a biohydrogen source were evaluated at intermediate temperature to achieve electrolysis. The components, such as holocellulose, cellulose, lignin, and extractives, were separated from Miscanthus sinensis to understand the reactions of Miscanthus sinensis in the electrolysis cell. The relatively high resistivity and low current-voltage performance of an electrolysis cell using lignin were responsible for degradation of the electrolysis properties compared to those with pure cellulose or holocellulose as biohydrogen resources. Biohydrogen was formed according to Faraday’s law and evolved continuously at 0.1 A cm⁻² for 3,000 seconds.