Electrosynthesis, activation, and applications of nickel-iron oxyhydroxide in (photo-)electrochemical water splitting at near neutral condition

Selective electrosynthesis of platform chemicals from the electrocatalytic reforming of biomass-derived hexanediol

6-Hydroxyhexanoic acid and adipic acid are platform chemicals and are widely used as building blocks for the synthesis of important polymers. Nevertheless, the industrial syntheses of these two chemicals are fossil fuel-based and involve the use of corrosive acid and emission of the NOx greenhouse gas. In this study, the electrosynthesis of 6-hydroxyhexanoic acid and adipic acid from the electrochemical oxidation of hexanediol at the nanoporous nickel oxyhydroxide modified electrode was explored as an environmentally-benign alternative to the industrial syntheses of 6-hydroxyhexanoic acid and adipic acid. The effects of electrolysis conditions, including the electrolyte pH and applied potentials, on faradaic efficiency and product distribution of the electrochemical oxidation of hexanediol, were thoroughly examined through a series of controlled-potential electrolyses. In addition, the scale-up electrosynthesis of 6-hydroxyhexanoic acid and adipic acid using a flow-type electrolyzer was also demonstrated.

Efficient Synthesis of α-FeOOH from Pickling Wastewater in Falling Film Tower and Its Kinetics

An efficient way to synthesize α-FeOOH from pickling wastewater in a falling film tower was proposed for the first time. This method overcomes the shortcomings of the traditional air oxidation method, and its production efficiency is increased by 16 times. The purity of α-FeOOH synthesized from pickling wastewater can reach 96.3%, and the iron recovery rate is greater than 90%. At the same time, we have systematically studied its kinetics in the falling film tower. The reaction rate constant k at different temperatures was also determined with the activation energy E _a = 32.2497 kJ/mol and the pre-exponential A = 47.4132 s^-1. In addition, based on the double-film theory, a corresponding macrokinetic model was established. Also, the Hatta number in the reaction system was obtained, which proved the excellent gas-liquid mass transfer performance in the falling film tower. This work provides a promising method for the efficient production of α-FeOOH and the recycling of pickling wastewater.