Effect of single-metal-atoms in electrovalorization of biomass and paired electrolysis

A pairing of cathodic electrochemical CO2 reduction reaction (eCO2RR) or hydrogen evolution reaction (HER) with the anodic electrochemical 5-hydroxymethylfurfural oxidation reaction (eHMFOR) has emerged with numerous scopes by offering high current density and product selectivity with lower energy input. However, the main hurdle that remains is to develop effective electrode materials for the simultaneous cathodic reduction and anodic oxidation of HMF/furfural/glycerol. We have showcased single-metal-atoms containing electrodes with adsorption sites operating at the atomic scale for eHMFOR under lower cell voltage. Atomic-scale cooperative adsorption sites energetically favor eHMFOR under minimum cell voltage in an integrated electrolysis system in which single-metal-atom sites and heteroatom can facilitate surface electronic exchange and transfer capabilities with the adsorbate. The electrochemical anodic oxidation and reduction of biomass-derived furans (e. g. furfural, 5-hydroxymethyl furfural, glycerol) by using single-metal-atom electrodes accelerate adsorption of oxygenate substrates and intermediates to construct the desired form of electrolysis with concurrent cathodic eCO2RR, oxygen evolution reaction (OER), and HER. We describe electrolytic oxidation/reduction at low energy consumption followed by a comparative analysis of H-cell and flow-cell systems for accelerated electrovalorization. The significance of maximum atom utilization of single-metal-atom is depicted. The difference in atomic-site-driven electrolysis of biomass-derived furans with that of the conventional electrodes is reviewed with specific attention to the effect of atomic-sites, defect-driven process, and paired electrolysis. Meanwhile, major focus is given to the flow-cell-based electrovalorization for HMFOR by enhancing the role of atomic and electronics of single-metal-atom electrodes. The key issues to achieve high selectivity and Faradaic efficiency from the coupling of eCO2RR/HER with HMFOR with desired energy conversion are discussed. Finally, a perspective on electrovalorization for better selectivity towards products from biomass is included.