Synthesis of carbon nitrides from carbon dioxide

Provided are methods of converting carbon dioxide to carbon nitrides. In a first reaction, carbon dioxide may be reacted with metal nitrides, such as Li.sub.3N, to form carbon nitrides in a fast and exothermic reaction. Also provided are methods of using product metal cyanamides from the first reaction to subsequently generate additional carbon nitrides.https://digitalcommons.mtu.edu/patents/1005/thumbnail.jp

MoS2 as a co-catalyst for photocatalytic hydrogen production from water

Solar-to-hydrogen conversion based on photocatalytic water splitting is a promising pathway for sustainable hydrogen production. The photocatalytic process requires highly active, inexpensive, and earth-abundant materials as photocatalysts. As a presentative layer-structured transition metal dichalcogenides, molybdenum disulfide (MoS2) is attracting intensive attention due to its unique electro and photo properties. In this article, we comprehensively review the recent research efforts of exploring MoS2 as a co-catalyst for photocatalytic hydrogen production from water, with emphasis on its combination with CdS, CdSe, graphene, carbon nitride, TiO2, and others. It is shown that MoS2–semiconductor composites are promising photocatalysts for hydrogen evolution from water under visible light irradiation

Degradation issues and stabilization strategies of protonic ceramic electrolysis cells for steam electrolysis

Protonic ceramic electrolysis cells (PCECs) are attractive electrochemical devices for converting electrical energy to chemicals due to their high conversion efficiency, favorable thermodynamics, fast kinetics, and inexpensive materials. Compared with conventional oxygen ion-conducting solid oxide electrolysis cells, PCECs operate at a lower operating temperature and a favorable operation mode, thus expecting high durability. However, the degradation of PCECs is still significant, hampering their development. In this review, the typical degradations of PCECs are summarized, with emphasis on the chemical stability of the electrolytes and the air electrode materials. Moreover, the degradation mechanism and influencing factors are assessed deeply. Finally, the emerging strategies for inhibiting long-term degradations, including chemical composition modifications and microstructure tuning, are explored

Thermo-photo catalytic anode process for carbonate-superstructured solid fuel cells

Converting hydrocarbons and greenhouse gases (i.e., carbon dioxide, CO2) directly into electricity through fuel cells at intermediate temperatures (450 to 550 °C) remains a significant challenge, primarily due to the sluggish activation of C-H and C=O bonds. Here, we demonstrated a unique strategy to address this issue, in which light illumination was introduced into the thermal catalytic CO2reforming of ethane in the anode as a unique thermo-photo anode process for carbonate-superstructured solid fuel cells. The light-enhanced fuel activation led to excellent cell performance with a record-high peak power density of 168 mW cm-2at an intermediate temperature of 550 °C. Furthermore, no degradation was observed during ~50 h operation. Such a successful integration of photo energy into the fuel cell system provides a new direction for the development of efficient fuel cells

Recent advances in graphene-based materials for fuel cell applications

The unique chemical and physical properties of graphene and its derivatives (graphene oxide, heteroatom-doped graphene, and functionalized graphene) have stimulated tremendous efforts and made significant progress in fuel cell applications. This review focuses on the latest advances in the use of graphene-based materials in electrodes, electrolytes, and bipolar plates for fuel cells. The understanding of structure-activity relationships of metal-free heteroatom-doped graphene and graphene-supported catalysts was highlighted. The performances and advantages of graphene-based materials in membranes and bipolar plates were summarized. We also outlined the challenges and perspectives in using graphene-based materials for fuel cell applications

Temperature, pressure, and adsorption dependent redox potentials: III. Processes of CO conversion to value-added compounds

Carbon monoxide (CO) is a primary air pollutant and a poisonous species for human beings, animals, and some catalytic reactions. Meanwhile, CO is also a versatile feedstock in the chemical industry to produce high‐value chemicals and clean fuels, which has stimulated extensive research interests in exploiting efficient CO conversion processes. Redox potential is a key thermodynamic quantity in these processes whereas only standard reduction potentials at 25°Cand 1 atm are currently available. Herein, it is the first time to report the effects of temperature (0–1000°C), pressure (1–100 atm), and adsorption on the redox potentials of 18 CO conversion reactions to form carbon dioxide, methane, straight‐chain alkanes (ethane, propane, and butane), light olefins(ethylene, propylene, and butylene), benzene, alcohols, aldehydes, acids, and dimethyl ether, based on theoretical calculations. It was noticed that gas‐phase, aqueous‐phase, and adsorption‐state redox potentials decrease with increasing temperature at an increased rate while they show different responses to pressure change. Namely, gas‐phase and most aqueous‐phase redox potentials increase with pressure at a gradually declined rate, while adsorption‐state redox potentials are not influenced by pressure. Most importantly, the significant differences up to 2.06 V under varied conditions highlight the necessity of applying operando redox potentials for CO conversion reactions

Degradation issues and stabilization strategies of protonic ceramic electrolysis cells for steam electrolysis

Protonic ceramic electrolysis cells (PCECs) are attractive electrochemical de-vices for converting electrical energy to chemicals due to their high conversion efficiency, favorable thermodynamics, fast kinetics, and inexpensive materials. Compared with conventional oxygen ion- conducting solid oxide electrolysis cells, PCECs operate at a lower operating temperature and a favorable operation mode, thus expecting high durability. However, the degradation of PCECs is still significant, hampering their development. In this review, the typical degradations of PCECs are summarized, with emphasis on the chemical stability of the electrolytes and the air electrode materials. Moreover, the degradation mechanism and influencing factors are assessed deeply. Finally, the emerging strategies for inhibiting long- term degradations, including chemical composition modifications and microstructure tuning, are explored

Carbonate-superstructured solid fuel cells with hydrocarbon fuels

A basic requirement for solid oxide fuel cells (SOFCs) is the sintering of electrolyte into a dense impermeable membrane to prevent the mixing of fuel and oxygen for a sufficiently high open-circuit voltage (OCV). However, herein, we demonstrate a different type of fuel cell, a carbonate-superstructured solid fuel cell (CSSFC), in which in situ generation of superstructured carbonate in the porous samarium-doped ceria layer creates a unique electrolyte with ultrahigh ionic conductivity of 0.17 S.cm21 at 550 °C. The CSSFC achieves unprecedented high OCVs (1.051 V at 500 °C and 1.041 V at 550 °C) with methane fuel. Furthermore, the CSSFC exhibits a high peak power density of 215 mW.cm22 with dry methane fuel at 550 °C, which is higher than all reported values of electrolyte-supported SOFCs. This provides a different approach for the development of efficient solid fuel cells