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 (CuCl 2 , CrCl 3 and FeCl 3 ) are studied as the synergistic catalysts with POM to promote the degradation of raw biomass. Notably, FeCl 3 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.