Unraveling a bifunctional mechanism for methanol-to-formate electro-oxidation on nickel-based hydroxides

Abstract

For nickel-based catalysts, in-situ formed nickel oxyhydroxide has been generally believed as the origin for anodic biomass electro-oxidations. However, rationally understanding the catalytic mechanism still remains challenging. In this work, we demonstrate that NiMn hydroxide as the anodic catalyst can enable methanol-to-formate electro-oxidation reaction (MOR) with a low cell-potential of 1.33/1.41 V at 10/100 mA cm−2, a Faradaic efficiency of nearly 100% and good durability in alkaline media, remarkably outperforming NiFe hydroxide. Based on a combined experimental and computational study, we propose a cyclic pathway that consists of reversible redox transitions of NiII-(OH)2/NiIII-OOH and a concomitant MOR. More importantly, it is proved that the NiIII-OOH provides combined active sites including NiIII and nearby electrophilic oxygen species, which work in a cooperative manner to promote either spontaneous or non-spontaneous MOR process. Such a bifunctional mechanism can well account for not only the highly selective formate formation but also the transient presence of NiIII-OOH. The different catalytic activities of NiMn and NiFe hydroxides can be attributed to their different oxidation behaviors. Thus, our work provides a clear and rational understanding of the overall MOR mechanism on nickel-based hydroxides, which is beneficial for advanced catalyst design.

Mechanistic Investigations of Electrochemical Ethanol Oxidation Reaction by In Situ Raman Spectroscopy

“…The role of M 2 + /M 3 + as catalytic centers for EOR was further validated by subsequent studies. [50,55] Chen et al observed analogous results via in situ Raman spectroscopy and further evidenced the activity of NiOOH through isotope labelling with time-of-flight secondary ion mass spectrometry (TOF-SIMS). [49] As depicted in Figure 5b-c, the delay in the Raman signal for NiOOH was also identified with the presence of ethanol for β-Ni(OH) 2 .…”

Boosting nucleophilic attack to realize high current density biomass valorization on a tunable Prussian blue analogue

“…, hydroxyl and aldehyde). 45 The nucleophilic groups are in electron-rich states. The CN stretching vibration can be regarded as a fingerprint for cyanide-based coordination compounds.…”

Emerging on-chip microcells in electrocatalysis: functions of window and circuit

“…, H 2 , C2–C4 products, NH 3 , and CH 3 OH) using renewable electricity, has received increasing interest recently. 7–12 Being different from thermo- or photo-catalysis, electrocatalysis usually involves two charge processes: one is the charge flowing from the substrate to the catalyst and then to the catalyst-electrolyte interface; the other is charge transfer at the interface, finally making the reaction happen. Briefly, the former refers to an electronic process where the catalyst should be conductive.…”