Electrocatalytic Oxidation of Formic Acid: Closing the Gap Between Fundamental Study and Technical Applications

Resolving the chemical identity of H2SO4 derived anions on Pt(111) electrodes: they're sulfate

Understanding how electrolyte composition controls electrocatalytic reactions requires molecular-level insight into electrode/electrolyte interaction. Perhaps the most basic aspect of this interaction, the speciation of the interfacial ion, is often controversial for even relatively simple systems. For example, for Pt(111) in 0.5 M H₂SO₄ it has long been debated whether the adsorbed anion is SO₄^2-, HSO₄^- or an H₃O⁺SO₄^2- ion pair. Here we apply interface-specific vibrational sum frequency (VSF) spectroscopy and theory to this problem and perform an isotope exchange study: we collect VSF spectra of Pt(111) in H₂SO₄(H₂O) and D₂SO₄(D₂O) as a function of bias and show that at all potentials they are identical. This is the most direct spectroscopic evidence to date that SO₄^2- is the dominant adsorbate, despite the fact that at 0.5 M H₂SO₄ bulk solution is dominated by HSO₄^-. This approach is based on the unique selection rule of the VSF spectroscopy and thus offers a new way of accessing general electrode/electrolyte interaction in electrocatalysis.

Electrochemical Hydroxylation of Arenes Catalyzed by a Keggin Polyoxometalate with a Cobalt(IV) Heteroatom

The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol, is an important research challenge. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates, which are easily hydrolyzed by water to yield the corresponding phenols, is presented. The formylation reaction occurs on a Pt anode in the presence of [Co^III W₁₂ O₄₀ ]^5- as a catalyst and lithium formate as an electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR. Hydrogen was formed at the Pt cathode. The sum transformation is ArH+H₂ O→ArOH+H₂ . Non-optimized reaction conditions showed a Faradaic efficiency of 75 % and selective formation of the mono-oxidized product in a 35 % yield. Decomposition of formic acid into CO₂ and H₂ is a side-reaction.

Carbon dioxide activation and transformation to HCOOH on metal clusters (M = Ni, Pd, Pt, Cu, Ag & Au) anchored on a polyaniline conducting polymer surface – an evaluation study by hybrid density functional theory

Computational electrocatalytic reduction of CO₂ to HCOOH was achieved on different metal-anchored polyaniline using density functional theory. Cu was found to perform better than other metals at an applied potential −0.58 V through the H*COO pathway.