Low‐Energy Catalytic Electrolysis for Simultaneous Hydrogen Evolution and Lignin Depolymerization

Abstract

Here, a new proton-exchange-membrane electrolysis is presented, in which lignin was used as the hydrogen source at the anode for hydrogen production. Either polyoxometalate (POM) or FeCl was used as the catalyst and charge-transfer agent at the anode. Over 90 % Faraday efficiency was achieved. In a thermal-insulation reactor, the heat energy could be maintained at a very low level for continuous operation. Compared to the best alkaline-water electrolysis reported in literature, the electrical-energy consumption could be 40 % lower with lignin electrolysis. At the anode, the Kraft lignin (KL) was oxidized to aromatic chemicals by POM or FeCl , and reduced POM or Fe ions were regenerated during the electrolysis. Structure analysis of the residual KL indicated a reduction of the amount of hydroxyl groups and the cleavage of ether bonds. The results suggest that POM- or FeCl -mediated electrolysis can significantly reduce the electrolysis energy consumption in hydrogen production and, simultaneously, depolymerize lignin to low-molecular-weight value-added aromatic chemicals.

Hydrogen Production by Direct Lignin Electrolysis at Intermediate Temperatures

“…Another important result was the onset voltage of ca . 0.25 V at all the tested temperatures, which was comparable to those reported for direct ethanol electrolysis, and much lower than those reported for indirect lignin electrolysis . Figure (b) shows hydrogen evolution rates from the cathode at various temperatures, including the theoretical values calculated using Faraday's law, based on the two‐electron reaction represented in Reaction (4).…”

Low‐temperature, Low‐Energy, and High‐Efficiency Pretreatment Technology for Large Wood Chips with a Redox Couple Catalyst

“…C1 (CÀCo rC ÀH) arise mainly because of lignin and extractives, C2 (CÀO) and C3 (C=O) are the predominant linkages in cellulose, and holocellulosew as rich in C2 and O2. [51] The proportion of CÀO and C=Ob onds increased and the proportion of C=C( or CÀC) bonds decreaseda fter the pretreatment, which may be because of the oxidation of CÀC( or C=C) bonds on the surface to CÀOa nd C=Ob onds by FeCl 3 /NaNO 3 . The O1sp eaks for HW and SW were also deconvoluted into three categories:O 1( C =O), O2 (CÀO), and O3 (O=CÀOR).…”

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

“…[160] Amaximum hydrogen production rate of 0.45 mmol s À1 was obtained. Du et al [140] reported the simultaneous electrooxidation of Kraft lignin to value-addedc hemicals at ag raphite-felt anode and the cogeneration of hydrogen gas at aP t/graphite cathode in ap rotone xchange membrane (PEM) electrochemical cell using ap olyoxometalate (POM) phosphomolybdic acid (H 3 PMo 12 O 40 denoted as PMo 12 )o rF eCl 3 as catalyst and chargetransfer mediators. For both POM and FeCl 3 ,o ver 90 %c urrent efficiency was reported while the energy consumption was re-duced by 40 %i nc omparison to the best reported PEM electrolysis energy consumption.…”

“…at 100 8Ca fter 18 h. Increasing the temperature to 190 8C for 1h resulted in 26.6 %o ft he solid lignin being oxidized to low-molecular-weight compounds. [140] NaderiNasrabadi et al developed ae lectrolyzer for biomass depolarization that can electrooxidize lignin-rich biorefinery waste to produce high-purity (97.6 %) hydrogen gas at mild conditions (room temperaturea nd atmosphericp ressure) using Ni-Co/TiO 2 on carbon paper anode. [161] At ap otential lower than 1.5 V, regardless of the temperature, lignin oxidation was thermodynamically favored over the OER whilea bove 1.5 VO ER was kinetically easier to achievet han lignin oxidation.…”