Temperature-Dependent Electrosynthesis of C₂Oxygenates from Oxalic Acid Using Gallium Tin Oxides

Abstract

The electrosynthesis of multi-carbon chemicals such as glyoxylic acid (GX) and glycolic acid (GC) from oxalic acid (OA) offers a feasible pathway to achieve sustainable chemical production, especially when coupled with the electroreduction of CO2 to form OA. Here, we demonstrate a series of gallium tin oxide catalysts for selective, controlled OA electroreduction to GX and GC in acidic media. The product distribution can be tuned by changing the reaction temperatures. At room temperature using the GaSnO x /C catalyst, GX can be obtained with a GX Faradaic efficiency (FEGX) of 92.7% at −0.7 V vs RHE and a GX current density (j GX) of −100.2 mA cm–2. At a raised temperature of 80 °C using the GaSnO x /C catalyst, a GC Faradaic efficiency (FEGC) of 91.7% at −0.8 V vs RHE can be obtained. The accelerated OA electroreduction results from the Ga/Sn synergy in the catalysts. A proper Ga/Sn ratio not only enriches OA adsorption and enhances surface binding of intermediates, but also ensures catalyst stability in acidic media.

Highly Efficient Electrosynthesis of Glycine over an Atomically Dispersed Iron Catalyst

“…NO 2 – is the main product of NO 3 – RR over the N–C-700 catalyst, which indicates that the Fe–N configuration is crucial for producing NH 2 OH to realize the C–N coupling. As mentioned above, GX is the key intermediate in the process of glycine formation; however, it can be over-reduced to GC. , During the OARR, production of GX suppresses that of GC at −0.9 V versus RHE over the N–C-700 catalyst (Figure S20). In contrast, N–C-600 with a lower pyrrolic N content of 2.49 atom % (Figure S21) exhibits a lower FE GX than N–C-700 (Figure S22), evincing that a rich pyrrolic N content could facilitate the OARR to GX.…”

“…The Eyring plots and Arrhenius plots of the formation of GX and GC over N–C-700 were used to determine the activation parameters of the OARR (Figure d, Figure S23, and Table S2). ,, The standard activation enthalpy (Δ r ≠ H m θ ), standard activation entropy (Δ r ≠ S m θ ), and activation energy ( E a ) of GX and GC formation were calculated. The smaller energy barrier for GX formation (Δ r ≠ H m θ = 26.2 kJ mol –1 , Δ r ≠ S m θ = −144.2 J mol –1 K –1 ) than GC formation (Δ r ≠ H m θ = 44.1 kJ mol –1 , Δ r ≠ S m θ = −98.4 J mol –1 K –1 ) over the N–C-700 catalyst suggests that the conversion of OA to GX is more facile than that of OA to GC.…”

“…The Eyring plots and Arrhenius plots of the formation of GX and GC over N−C-700 were used to determine the activation parameters of the OARR (Figure 3d, Figure S23, and Table S2). 16,34,35 The standard activation enthalpy (Δ r ≠ H m θ ), standard activation entropy (Δ r ≠ S m θ ), and activation energy (E a ) of GX and GC formation were calculated. The smaller energy barrier for GX formation (Δ r These results indicate that abundant pyrrolic N and the FeN 3 C structure in Fe−N−C-700 are the main factors for accelerating the GX formation kinetics and suppressing further reduction of GX, which ensures the presence of an excess GX for the coupling with NH 2 OH to produce GAO.…”

“…From an economic perspective, using upstream carbonaceous molecules as reactants could offer a cost-competitive route for amino acid production with a reduced number of chemical production steps. Oxalic acid (OA) is a highly electrochemical reactive reagent , and could be obtained from CO 2 or biomass transformation, such as CO 2 electroreduction and glucose oxidation . OA can be selectively electro-reduced to GX, , which could further react with NH 2 OH to produce glycine. , However, this C–N coupling process involves multiple electron and proton transfer steps, which increases the possibility of side reactions, thus decreasing the selectivity toward glycine.…”

“…Oxalic acid (OA) is a highly electrochemical reactive reagent , and could be obtained from CO 2 or biomass transformation, such as CO 2 electroreduction and glucose oxidation . OA can be selectively electro-reduced to GX, , which could further react with NH 2 OH to produce glycine. , However, this C–N coupling process involves multiple electron and proton transfer steps, which increases the possibility of side reactions, thus decreasing the selectivity toward glycine.…”