Non-precious metal nanoparticle electrocatalysts for electrochemical modification of lignin for low-energy and cost-effective production of hydrogen

The electrochemical oxidation of lignin waste from pulping mills and biorefineries represents a potentially renewable process for generating hydrogen for energy storage with co-generation of industrial chemicals. Such a process could significantly reduce the cost of generating hydrogen by 1) a low voltage (low energy) anodic oxidation process and 2) generation of value-added chemicals that can be sold. To date, the electrochemical oxidation of large organic molecules like lignin has mainly been investigated on either expensive metals like platinum or on bulk metal electrodes (i.e., large, flat electrodes). Nanoparticle electrocatalysts, though, enhance the surface area available for electrochemical reactions and may lead to improved mass transport of reactants and products through the electrocatalyst layer. In addition, nanoparticle electrocatalysts allow for unique alloying and synergistic effects between different metals. We report here on non-precious metal nanoparticle electrocatalysts for the oxidation of lignin in alkaline media, and show that lignin oxidation occurs at lower voltages than oxygen evolution. Such results are a first step toward demonstrating that lignin oxidation at lower overpotentials than required for oxygen evolution could lead to efficient generation of hydrogen. We present 1) electrochemical evidence of lignin oxidation in alkaline media and 2) spectroscopic evidence of electrochemical modification of the lignin biopolymer.