Electrochemical hydrogenation of levulinic acid, furfural and 5-hydroxymethylfurfural

Platform molecules from lignocellulosic biomass, such as levulinic acid (LA), furfural (FF), and 5-hydroxymethylfurfural (HMF), hold great potentials as precursors to various fuels and high-value compounds through catalytic hydrogenation. However, the existing thermochemical conversions of these carbonyl-containing short-chain organics such as thermal catalytic hydrogenation involve energy-intensive and expensive processes. Electrocatalytic hydrogenation (ECH) emerges as an environmentally friendly, cost-effective, and safe process. The ECH of these organics can contribute to mitigating fossil-energy dependencies, fostering sustainable energy production, and yielding socio-economic benefits. ECH of these organics are thus intriguing, but there is a need to objectively evaluate this field. This review summarizes the product outcomes and critical reaction parameters (e.g., electrode materials, temperatures, electrolyte compositions) associated with ECH of LA, FF, and HMF. Emphasis is placed on the mechanisms related to the varying substrates. Special attention was paid to the correlations of catalytic performance with catalyst structures. After a thorough literature survey, strategies for catalyst design are discussed to enhance selectivity by promoting desired product formation and suppressing competing reactions. Moreover, current challenges, unresolved issues, and future perspectives on ECH of LA, FF, and HMF are proposed. It is expected that this work will afford useful information on the synthesis of electrocatalysts for electrochemical conversions of biomass.