Cobalt–metalloid alloys for electrochemical oxidation of 5-hydroxymethylfurfural as an alternative anode reaction in lieu of oxygen evolution during water splitting

Abstract

The electrochemical water splitting commonly involves the cathodic hydrogen and anodic oxygen evolution reactions (OER). The oxygen evolution reaction is more energetically demanding and kinetically sluggish and represents the bottleneck for a commercial competitiveness of electrochemical hydrogen production from water. Moreover, oxygen is essentially a waste product of low commercial value since the primary interest is to convert electrical energy into hydrogen as a storable energy carrier. We report on the anodic oxidation of 5-hydroxymethylfurfural (HMF) to afford the more valuable product 2,5-furandicarboxylic acid (FDCA) as a suitable alternative to the oxygen evolution reaction. Notably, HMF oxidation is thermodynamically more favorable than water oxidation and hence leads to an overall improved energy efficiency for H2 production. In addition, contrary to the “waste product O2”, FDCA can be further utilized, e.g., for production of polyethylene 2,5-furandicarboxylate (PEF), a sustainable polymer analog to polyethylene terephthalate (PET) and thus represents a valuable product for the chemical industry with potential large scale use. Various cobalt–metalloid alloys (CoX; X = B, Si, P, Te, As) were investigated as potential catalysts for HMF oxidation. In this series, CoB required 180 mV less overpotential to reach a current density of 55 mA cm−2 relative to OER with the same electrode. Electrolysis of HMF using a CoB modified nickel foam electrode at 1.45 V vs RHE achieved close to 100% selective conversion of HMF to FDCA at 100% faradaic efficiency.

Prospects of Value‐Added Chemicals and Hydrogen via Electrolysis

“…Current densities up to hundreds of mA cm −2 were reported for both catalysts at potentials lower than 1.4 V, making HMF oxidation a promising anodic counter reaction for cathodic HER. In another study, Co‐based electrocatalysts showed 100 % conversion of HMF to FDCA with 90 % FE but at higher overpotentials than the Ni‐based electrocatalysts.…”

“…) and on CoB/NF (orange—dot line) (adapted with permission from Ref. ). b) Overview of alcohol electrooxidation reactions and important target products and their application domain.…”

Recent Advances in Electrochemical Hydrogen Production from Water Assisted by Alternative Oxidation Reactions

“…Especially in the recent years, some research groups highlighted promising potentials by integrating the HER with electrochemical HMF oxidation for simultaneous H 2 generation and oxidative HMF upgrading. [57][58][59][60] A representative advance in this research field was reported by Sun's group in 2016. [58] They demonstrated a bifunctional catalytic electrode based on 3D Ni 2 P nanoparticle arrays on Ni foam (Ni 2 P NPA/NF) to couple HMF oxidation and HER.…”

“…In this context, transition‐metal‐based electrocatalysts, especially compounds or alloys of Ni and Co with main‐group elements ( e. g., P and S) as well as layered double hydroxides (LDHs), were reported to be efficient electrocatalysts for the selective oxidation of HMF to target products, achieving high conversions and yields. Especially in the recent years, some research groups highlighted promising potentials by integrating the HER with electrochemical HMF oxidation for simultaneous H 2 generation and oxidative HMF upgrading …”

2,5-Furandicarboxylic acid production via catalytic oxidation of 5-hydroxymethylfurfural: Catalysts, processes and reaction mechanism

“…Driven by the electrochemical potential, more and more innovative and cheap catalysts developed from earth-abundant transition metals, such as Ni 2 P [133], CoP [134], Ni 2 S 3 [135], porous Ni [136], Ni x B [137], CoB [138], NiB x [139], NiCo 2 O 4 [140,141], VN [142], Ni 3 N@C [143], Ni/Co/Fe oxyhydroxides [144], Ni/NiOOH [145], nanocrystalline Cu foam [146], CuNi(OH) 2 /C [147], NiSe@NiO x [148], NiFe-LDH [127], and Cu x S@NiCo-LDH [149], were reported to be more efficient than noble metal catalysts, reversing the situation that the precious metal catalysts are more active and popular than the transition metal catalysts in HMF thermocatalytic oxidation. Grabowski et al [132] firstly reported the HMF electrooxidation into FDCA on NiOOH anode, realizing 71% FDCA yield with 84% faradaic efficiency (FE) in a divided H-shape electrolyzer with 1 M NaOH aqueous electrolyte.…”