Unraveling a bifunctional mechanism for methanol-to-formate electro-oxidation on nickel-based hydroxides.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36973279.
- Also identified by DOI 10.1038/s41467-023-37441-9 and PMC identifier 10042884.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
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<sup>-2</sup>, 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 Ni<sup>II</sup>-(OH)<sub>2</sub>/Ni<sup>III</sup>-OOH and a concomitant MOR. More importantly, it is proved that the Ni<sup>III</sup>-OOH provides combined active sites including Ni<sup>III</sup> 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 Ni<sup>III</sup>-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.