Glycerol is a byproduct of biodiesel production and an abundant feedstock for the synthesis of high-value chemicals. A promising approach for valorization of glycerol is electrooxidation on gold. In this work, we investigate electrooxidation of glycerol on gold in acidic media using cyclic voltammetry and density functional theory calculations. Experimentally, we observe activity for electrooxidation above a potential of 0.5 V versus the reversible hydrogen electrode (RHE). A Pourbaix diagram is calculated to evaluate the surface coverage under reaction conditions, indicating that the surface is free from adsorbates at the measured onset potential. Computationally, we find that the onset potentials for partial dehydrogenation of glycerol to dihydroxyacetone, 2,3-dihydroxy-2-propenal, and glyceraldehyde are 0.39, 0.39, and 0.60 V versus RHE, respectively, while complete dehydrogenation to carbon monoxide requires 0.50 V versus RHE. Our theoretical and experimental findings are in agreement and show the possibility of using gold as a catalyst for the production of hydrogen and other valuable chemicals from glycerol.

Glycerol exists in large amounts owing to its role as a byproduct in biodiesel production, and thanks to its chemical composition, it can be converted into more high-value products, such as mono-and polyethers, esters, diols, acrolein, and others. Hence, predicting glycerol-reactive properties is of utmost importance for designing efficient catalytic processes for its selective (electro)catalytic transformations; however, such an understanding is still far from complete. In this work, we performed quantum chemical calculations to validate a range of dispersion-corrected functionals to accurately predict and interpret structural, electronic, and vibrational properties of glycerol adsorbed on bare and transition-metal surface-alloyed Au(111) surface. optB86b-vdW (van der Waals) was found to have the overall best agreement with experiments concerning lattice constant, bulk stress, surface energy, and methanol adsorption among PBE (Perdew−Burke−Ernzerhof), optB88-vdW, optPBE-vdW, vdW-DF (density functional), vdW-DF2 (density functional 2nd version), and vdW-BEEF (Bayesian error estimation functional). Glycerol adsorption energy is found to correlate well with the calculated d-band center of the transition-metalcontaining Au(111) surface layer. O−H stretching vibrations are found to be very sensitive of the surface-alloy atom and resulted in large shifts toward lower wavenumbers, when compared to those on bare Au(111). The latter results clearly show that adsorption of glycerol to surface-alloy atoms can be monitored in situ by infrared spectroscopy.

Glycerol is a byproduct of biodiesel production and an abundant feedstock that can be used for the synthesis of highvalue chemicals. There are many approaches for glycerol valorization, but, due to the complicated reaction mechanism, controlling which products are produced is challenging. Here, we describe glycerol's chemical selectivity for different metallic catalysts using descriptors for carbon (mainly *C, *CH 2 OH) and oxygen (mainly *O, CH 3 O*). The quality of these descriptors and the weighted combinations thereof are validated based on their fit, via linear regression, to the binding energies of all reaction intermediates generated in the first two glycerol dehydrogenation steps on a number of close-packed Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au surfaces. We show that *CH 2 OH is a better descriptor than *C for the studied carbon-bound intermediates, which is attributed to the observation that the adjacent *OH group interacts with the surface. This leads to a negative oxygen dependence, which can be generalized to similar alcohol-derived adsorbates. Furthermore, we show that CH 3 O* is a better oxygen descriptor than *O for the studied intermediates. This is mainly attributed to the difference between the single and double bonds, as we show that *OH is closer to the accuracy of CH 3 O*. Multilinear regression with different combinations of *C, *O, and *OH is comparable in accuracy to that of *CH 2 OH and CH 3 O*. Scaling relationships are used to determine the selectivity map for glycerol dehydrogenation. The results show that the first dehydrogenation is selective toward two different intermediates (one bonded via the secondary carbon and the other via the secondary oxygen) depending on the relative bond strength of the carbon and oxygen descriptors. The second dehydrogenation step results in five intermediates, again depending primarily on the relative bond strength of carbon and oxygen to the surface. The selectivity maps can be used together with kinetic considerations and experimental data to find catalyst candidates for glycerol dehydrogenation.

Glycerol is a byproduct of biodiesel production and an abundant feedstock for the synthesis of high-value chemicals. One promising approach for valorization of glycerol is electrooxidation yielding hydrogen and value-added products. However, due to the vast amount of intermediary steps and possible products, the process is not fully understood. Here, the first two deprotonations of glycerol on close-packed transition metals (Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au) are investigated using density functional theory calculations together with the computational hydrogen electrode. We find that the theoretical limiting potential for the studied reaction is close to 0 V vs the reversible hydrogen electrode, ranging from −0.12 V for ruthenium to +0.35 V for gold. Furthermore, the results show that Ru, Rh, Ir, Ag, and Au are selective toward dihydroxyacetone and its derivatives, while Pd and Pt are selective toward either dihydroxyacetone or glyceraldehyde and their derivatives, and that Cu, Co, and Ni are selective toward hydropyruvic acid. The results can be rationalized in terms of the relative bond strengths of carbon and oxygen on the metal. In addition, we find that solvent effects are generally small, the exceptions being the limiting potential on copper and the mechanism on rhodium. These results can be used to steer the selectivity toward more valuable products and thereby increase the economic yield of biodiesel production.

A detailed understanding of the methanol electrooxidation reaction mechanism is important for the further development of methanol fuel cells. By modeling the reaction on Au(111) using density functional calculations, we investigate the impact of solvent models, focusing on the potential-determining step and the theoretical limiting potential. Both implicit solvent effects, in the form of VASPsol, and explicit solvation by water molecules are investigated. The use of explicit water molecules changes the energetics of the reaction intermediates, and it requires the addition of six water molecules to reach converged results. An important observation is that the configuration space of the explicit water molecules needs to be treated carefully. Upon comparison of the most simple vacuum model with a more advanced combined solvent model, it is clear that there are some pronounced differences; for instance, both implicit solvent effects and explicit solvation stabilize HCOOH and destabilize CO2. There are, however, qualitative agreements between the models; for instance, the first deprotonation step of methanol is found to be the potential-determining step, although the more accurate model put forth aldehyde and formate formation as possible competitive steps. The results are experimentally validated by using cyclic voltammetry.