The escalating demand for fossil fuels has raised environmental concerns, urging the exploration of biosynthetic pathways for renewable hydrocarbon fuels. Terminal alkenes (α-alkenes) emerge as "drop-in" compatible fuels and chemicals, holding the potential to replace traditional fossil fuels. Fatty acid decarboxylases present a promising route for converting fatty acids into α-alkenes, underscoring the imperative need for comprehending the catalytic mechanisms governing these enzymes in the quest for renewable biofuel production. The reported fatty acid decarboxylases entail the involvement of heme and non-heme iron cofactors in the redox process. In this review, we summarize the reaction mechanisms of four iron-dependent fatty acid decarboxylases (OleTJE, OleTPRN, UndA, and UndB), providing a critical analysis of the factors influencing chemical selectivity and catalytic performance.

Herein, we report a phosphine free novel ruthenium NNN based pincer complex that can act as a highly efficient catalyst for N-methylation of amines and direct N-methylation of nitroarenes using methanol as a C1 source under mild reaction conditions following the borrowing-hydrogen approach.

Abstract

A novel phosphine-free ruthenium pincer complex based on an NNN pincer ligand has been prepared and fully characterized. The complex was subsequently employed as an efficient catalyst for the N-methylation of amines and the direct N-methylation of nitroarenes using methanol as a C1 source under mild reaction conditions following the borrowing-hydrogen approach. Both of the catalytic transformations were performed with only catalytic amounts of base under closed air conditions without using any other additives.

We report on the fixation of CO₂ to prebiotic intermediates over mesoporous silica-supported Co−Fe catalysts. Supported catalysts convert CO₂ to various gaseous and liquid products under simulated hydrothermal vent conditions. Among different catalysts, a supported Co−Fe alloy with the same composition as the natural mineral wairauite yields the highest concentrations of formate and acetate, which are key intermediates in the acetyl-coenzyme A pathway.

Abstract

To test the ability of geochemical surfaces in serpentinizing hydrothermal systems to catalyze reactions from which metabolism arose, we investigated H₂-dependent CO₂ reduction toward metabolic intermediates over silica-supported Co−Fe catalysts. Supported catalysts converted CO₂ to various products at 180 °C and 2.0 MPa. The liquid product phase included formate, acetate, and ethanol, while the gaseous product phase consisted of CH₄, CO, methanol, and C₂−C₇ linear hydrocarbons. The 1/1 ratio CoFe alloy with the same composition as the natural mineral wairauite yielded the highest concentrations of formate (6.0 mM) and acetate (0.8 mM), which are key intermediates in the acetyl-coenzyme A (acetyl-CoA) pathway of CO₂ fixation. While Co-rich catalysts were proficient at hydrogenation, yielding mostly CH₄, Fe-rich catalysts favored the formation of CO and methanol. Mechanistic studies indicated intermediate hydrogenation and C−C coupling activities of alloyed CoFe, in contrast to physical mixtures of both metals. Co in the active site of Co−Fe catalysts performed a similar reaction as tetrapyrrole-coordinated Co in the corrinoid iron-sulfur (CoFeS) methyl transferase in the acetyl-CoA pathway. In a temperature range characteristic for deeper regions of serpentinizing systems, oxygenate product formation was favored at lower, more biocompatible temperatures.

This review introduces the in-situ characterization techniques frequently used in the electrocatalytic NO₃ ⁻ reduction to NH₃ (ENO₃RA), summarizes five pathways for converting *NO to NH₃ during ENO₃RA on Cu-based catalysts. And the application of the in-situ techniques is presented as an example of Cu-based catalysts, which are sorted out in terms of composition and structure.

Abstract

The excess nitrate (NO₃ ⁻) in water mainly comes from agricultural fertilization and industrial wastewater, which breaks the nitrogen balance and poses a serious threat to the environment and human health. Driven by renewable energy, the electrocatalytic NO₃ ⁻ reduction to ammonia (NH₃) (ENO₃RA) is an environmentally friendly and sustainable technology. Due to its special structure, copper (Cu) is currently one of the best catalysts for ENO₃RA, but the reaction mechanism and the structure–activity relationships of catalysts are still not clear enough. In-situ characterization is a powerful tool to gain insight into the reaction process. This review introduces several types of in-situ techniques such as in-situ XAS, in-situ FTIR and in-situ DEMS, summarizes five pathways for converting *NO as the key intermediate to NH₃ during ENO₃RA on Cu-based catalysts. The research progress of Cu-based electrocatalysts in recent years is sorted out from the aspects of composition and structure, and the catalytic mechanisms are discussed with the help of in-situ characterization technologies. This review would be of help to provide reference characterization methods for exploring the mechanism and the design of electrocatalysts for ENO₃RA.

The development of base metal electrodes that can act as active and stable oxygen generating electrodes in water electrolysis systems, especially at low pH levels, remains a challenge. The use of suspensions as electrolytes for water splitting has until recently been limited to photoelectrocatalytic approaches. A high current density (j=30 mA/cm2) for water electrolysis has been achieved at a very low oxygen evolution reaction (OER) potential (E=1.36 V vs. RHE) using a SnO2/H2SO4 suspension-based electrolyte in combination with a steel anode. More importantly, the high charge-to-oxygen conversion rate (Faraday efficiency of 88% for OER at j=10 mA/cm2 current density). Since cyclic voltammetry (CV) experiments show that oxygen evolution starts at a low, but not exceptionally low, potential, the reason for the low potential in chronoamperometry (CP) tests is an increase in the active electrode area, which has been confirmed by various experiments. For the first time, the addition of a relatively small amount of solids to a clear electrolyte has been shown to significantly reduce the overpotential of the OER in water electrolysis down to the 100 mV region, resulting in a remarkable reduction in anode wear while maintaining a high current density.