Low-Cost Nanostructured Electrocatalysts for Hydrogen Evolution in an Anion Exchange Membrane Lignin Electrolysis Cell

Abstract

The aim of this study is to quantify the hydrogen production rate in an anion exchange membrane (AEM) lignin electrolysis cell. Two non-precious and nanostructured metal and metal oxide electrocatalysts were developed and used as the anodic catalysts in a lignin electrolysis process. H 2 production rates, energy consumption rates and faradaic efficiency were measured using β-PbO 2 /MWNTs and Ni-Co/TiO 2 electrocatalysts as the anode, where electrochemical depolymerization of lignin occurs. Our results were then compared with recent efforts for lignin electrolysis in the literature. This work demonstrates that the β-PbO 2 /MWNTs nanocomposite is the more stable and active electrocatalyst in this process. At the end, our results showed that using β-PbO 2 /MWNTs as the anodic electrocatalyst can enhance lignin oxidation rates, with a corresponding increase in the rate of H 2 production at the cathode. As a result, this can lead to high hydrogen evolution rates (∼45.6 mL/h), and increase energy efficiency by 20%, compared to a commercial alkaline water electrolyzer.

Electrochemical Lignin Conversion

“…45.6 ml h À 1 ) at the cathode in an anion exchange membrane (AEM) electrolysis cell, which reduced energy consumption by 20 % compared to commercial alkaline water electrolysis. [42] NiCo/TiO 2 as the anode electrocatalyst exhibited a similar effect. [43] Caravaca et al used polymer electrolyte membrane-based (PEM) reactors to perform the electrolysis of lignin-containing alkaline solutions in continuousflow mode for H 2 production with low electrical potentials (starting at ca.…”

“…Bateni et al loaded PbO 2 on MWCNTs to make a nanocomposite anode that showed superior catalytic activity and stability and enhanced lignin oxidation rates. [42] Furthermore, four IrO 2 -based MMO electrodes (Ti/SnO 2 À IrO 2 , Ti/RuO 2 À IrO 2 , Ti/Ta 2 O 5 À IrO 2 and Ti/TiO 2 À IrO 2 ) for lignin electrooxidation were fabricated by overlaying the binary metal oxides on pretreated Ti substrates. [55] The electrochemical studies revealed that: (i) the Ti/RuO 2 À IrO 2 electrode shows the highest stability and the highest activity for lignin depolymerization; (ii) the Ti/Ta 2 O 5 À IrO 2 electrode shows the best activity for oxygen evolution but worst activity for lignin depolymerization; (iii) the electrooxidation of lignin on all four IrO 2 -based electrode follows pseudo first-order kinetics.…”

“…However, the complex structure of lignin makes it very difficult to dissolve in common organic solvents. [82] Alkaline solutions (e. g., NaOH, KOH) have been widely used as the electrolyte in many lignin electrooxidation studies [10,31,44,48,59,[83][84][85][86][87][32][33][34]37,[40][41][42][43] due to increased solubility for lignin and high electron/ion conductivity. However, electrolysis in aqueous solution is limited by the water splitting reaction at 1.23 V, severely restricting the potential window for electrochemical reactions.…”

Greener Routes to Biomass Waste Valorization: Lignin Transformation Through Electrocatalysis for Renewable Chemicals and Fuels Production

“…Increasing lignin concentration up to 50 gL À1 was found to increase the reaction rate. Simultaneously, Bateni, et al [141] studied the hydrogen production in an anion-exchange membrane reactor using b-PbO 2 /MWNT( multi-walled carbon nanotube) in comparison to the NaderiNasrabadi's Ni-Co/TiO 2 electrocatalyst. Polarization and chronoamperometric studies indicated that b-PbO 2 /MWNTshowedh ighers tability,a ctivity,a nd enhanced reaction rates towards lignin oxidation and hydrogen gas cogeneration compared to Ni-Co/TiO 2 .…”

“…[141] They determined that higher initial lignin concentration (100 gL À1 )a nd higher anode catalyst loading (10 mg cm À2 )r esulted in improvedperformancef or lignin oxidation and hydrogen production and a2 0% improvement in energy efficiency when compared to commercial alkaline electrolyzers. [141]…”