Energy‐efficient Electrochemical Hydrogen Production Combined with Biomass Oxidation Using Polyoxometalate and Metal Salts

Abstract

Biomass oxidation in anode electrolyte solution is investigated for energy‐efficient hydrogen production. The redox of polyoxometalate (POM) as both biomass oxidation catalyst in the solution and charge carrier through regeneration at the graphite electrode promotes hydrogenation generation at the cathode, but suffers from a limited rate of biomass degradation due to the complex structure of solid lignocellulosic biomass. Herein, transition metal salts (CuCl2, CrCl3 and FeCl3) are studied as the synergistic catalysts with POM to promote the degradation of raw biomass. Notably, FeCl3 has the most significant effect in promoting the hydrolysis of cellulose by coordinating with the oxygen donor groups of carbohydrates and helps re‐oxidize reduced POM to maintain high oxidation ability of the solution. As a result, the faraday efficiency of hydrogen production at the cathode could reach 90 %. Coupling oxidation of biomass by contiguously recharged metal salts and POM with electrochemical hydrogen evolution, pure hydrogen source with improved economics is obtained at low energy consumption.

An Experimental Investigation of Hydrogen Production through Biomass Electrolysis

“…The results indicated that the electro-oxidation reaction occurred at the anode over the graphite electrode due to the Fe +3 /Fe +2 redox couple and that the reduced Fe +2 was reoxidised to Fe +3 , releasing electrons and protons [44]. During the pre-treatment of FeCl3 and glucose solution, Fe +3 was reduced to Fe +2 and glucose was oxidised [53]. Furthermore, the FeCl3-glucose solution changed from dark brown to dark red, confirming the degradation or oxidation of glucose.…”