Phosphomolybdic Acid as a Catalyst for Oxidative Valorization of Biomass and Its Application as an Alternative Electron Source

Abstract

Power-and solar-to-chemical energy conversion has been spotlighted as a promising technology for the efficient use of renewable energy resources. In principle, various chemicals can be sustainably produced through (photo)electrochemical reduction using water as a cheap and clean electron source. However, oxidation of water is a challenging task that results in low energy efficiency and reliability issues for the practical application of power-and solar-to-chemical energy conversion. Here, we show that various biomasses including lignin can be used as alternative electron sources. Electrons can be readily extracted from biomass using phosphomolybdic acid as a catalyst for oxidative depolymerization of biomass and an electron mediator at a much lower potential (0.95 V vs reversible hydrogen electrode) than water using best-performing but expensive catalysts (1.5−1.6 V). In particular, valueadded chemicals such as CO and vanillin are produced as by-products upon oxidative depolymerization of lignin. As a result, this approach allows efficient (photo)electrochemical production of hydrogen with a Faradaic efficiency close to unity at acidic pHs and brings additional economic benefits from by-products.

Bifunctional Electrolyzation for Simultaneous Organic Pollutant Degradation and Hydrogen Generation

“…Urea and biomass are the most widely studied agents . Such hybrid electrolysis systems that combine the anodic oxidation of organics and hydrogen production have merits of simultaneous wastewater treatment and production of high value-added chemicals …”

“…9 Such hybrid electrolysis systems that combine the anodic oxidation of organics and hydrogen production have merits of simultaneous wastewater treatment 10 and production of high value-added chemicals. 11 Complete mineralization of organic pollutants by oxidation is a research hotspot in environmental engineering. 12,13 Although electrooxidation of the organics such as drugs, 14−16 landfill leachate, 17 perfluorochemical, 18 phenolics, 19 and dye 20 has been widely reported, 21 their large-scale application is still limited by the low reaction rate and efficiency caused by the electrode fouling.…”

Porous framework-based hybrid materials for solar-to-chemical energy conversion: from powder photocatalysts to photoelectrodes

“…Despite these challenges, we believe that MOF-and COFbased materials with their own unique properties can provide insights into the design of and contribute to the practical application of solar-to-chemical energy conversion devices. Based on recent progress and understanding of photocatalytic OER, HER, and CO2RR by MOFs and COFs, one can also find their application in photocatalytic nitrogen reduction reaction, 238,239 biomass valorization, 240,241 etc.…”

Progress and Perspectives in Photo‐ and Electrochemical‐Oxidation of Biomass for Sustainable Chemicals and Hydrogen Production

“…Present as the most and second abundant source of biomass, cellulose, and lignin are considered the most attractive proton and carbon source due to their availability and low-cost. Biomass electrolysis of these raw feedstocks, lignin, [271][272][273][274][275] and cellulose [276,277] has therefore also been studied. Similar to methanol and ethanol electrolysis, the primary focus on lignin and cellulose electrolysis is H 2 production with less electricity consumption.…”

“…[480,481] Lignin oxidation and depolymerization products, such as vanillin and other benzyl alcohols, could also add to the technical and commercial values of the production stream. [271][272][273] Hibino et al demonstrated the possibility of using waste biomass raw materials, such as bread residue, cypress sawdust, rice chaff, and newspapers for H 2 evolution in an electrolysis cell achieving ≈100% H 2 at the cathode with a yield of 0.1-0.2 g H 2 per 1 g raw materials used. [482,483]…”