Electrocatalytic Glycerol Conversion: A Low-Voltage Pathway to Efficient Carbon-Negative Green Hydrogen and Value-Added Chemical Production

Abstract

Electrochemical glycerol oxidation reaction (GLYOR) could be a promising way to use the abundantly available glycerol for production of value-added chemicals and fuels. Completely avoiding the oxygen evolution reaction (OER) with GLYOR is an evolving strategy to reduce the overall cell potential and generate value-added chemicals and fuels on both the anode and cathode. We demonstrate the morphology-controlled palladium nanocrystals, afforded by colloidal chemistry, and their established morphology-dependent GLYOR performance. Although it is known that controlling the morphology of an electrocatalyst can modulate the activity and selectivity of the products, still it is a relatively underexplored area for many reactions, including GLYOR. Among nanocube (Pd-NC), truncated octahedron (Pd-TO), spherical and polycrystalline (Pd-PC) morphologies, the Pd-NC electrocatalyst deposited on a Ni foam exhibits the highest glycerol conversion (85%) along with 42% glyceric acid selectivity at a low applied potential of 0.6 V (vs reversible hydrogen electrode (RHE)) in 0.1 M glycerol and 1 M KOH at ambient temperature. Owing to the much favorable thermodynamics of GLYOR on the Pd-NC surface, the assembled electrolyzer requires an electricity input of only ∼3.7 kWh/m 3 of H 2 at a current density of 100 mA/cm 2 , in contrast to the requirement of ≥5 kWh/m 3 of H 2 with an alkaline/PEM electrolyzer. Sustainability has been successfully demonstrated at 10 and 50 mA/cm 2 and up to 120 h with GLYOR in water and simulated seawater.

Design of Bi-functional mixed oxide electrodes for selective oxidative C–C cleavage of glycerol to formate and synchronized green hydrogen production

“…The present work is complimentary to a recent work based on different morphologies of Pd employed as the electrocatalyst and operating at a significantly lower potential, but produces a mixture of acids. 63 This work offers a non-noble metal oxide electrocatalyst, NCMO/NF, for a practical, energy-efficient, and potentially commercially viable system for generating H 2 and formate. Moreover, the catalyst is stable enough to operate at a higher current density.…”

A review on the recent advances in the design and structure–activity relationship of TiO2-based photocatalysts for solar hydrogen production

“…227,228 Renewable H 2 production coupled with wastewater treatment with a suitable photocatalyst is another way to compensate for the energy loss at the expense of waste minimization. Renewable H 2 production and the concurrent formation of value-added products by employing a waste biomass component, such as glycerol, 52,212 are an attractive way to minimize waste with concurrent value addition. The oxidation of biomass components occurs at a significantly lower potential than oxygen formation; in addition, electrons and holes are simultaneously used ensure the catalyst stability for a longer period.…”

“…It should also be noted that a similar concept in the electrolysis of aqueous glycerol has been growing rapidly in the last 3–4 years and a few recent works is worth mentioning. Chauhan et al 212 achieved a low-voltage pathway to water electrolysis, while producing H 2 at the cathode and value-added products at the anode.…”

Electrocatalytic and Selective Oxidation of Glycerol to Formate on 2D 3d-Metal Phosphate Nanosheets and Carbon-Negative Hydrogen Generation

“…To date, the catalysts used for the glycerol oxidation reaction (GLYOR) have been primarily limited to noble metal-based catalysts, like Au, AuPt, Pt, Pd, PtSb, and PtRuSn, and non-noble metal-based catalysts, like NiOOH, − amorphous CoO x , NiCo 2 O 4 /NF, Co-doped Ni–Fe, CuCo 2 O 4 , and Ni 0.33 Co 0.67 (OH) 2 @HOS/NF . However, the reaction pathways of GLYOR are intricate, resulting in the production of various C1–C3 intermediates due to the difficulties in efficient C–C bond cleavage.…”