Combination of Highly Efficient Electrocatalytic Water Oxidation with Selective Oxygenation of Organic Substrates using Manganese Borophosphates

Abstract

One of the key catalytic reactions for life on earth, the oxidation of water to molecular oxygen, occurs in the oxygen‐evolving complex of the photosystem II (PSII) mediated by a manganese‐containing cluster. Considerable efforts in this research area embrace the development of efficient artificial manganese‐based catalysts for the oxygen evolution reaction (OER). Using artificial OER catalysts for selective oxygenation of organic substrates to produce value‐added chemicals is a worthwhile objective. However, unsatisfying catalytic performance and poor stability have been a fundamental bottleneck in the field of artificial PSII analogs. Herein, for the first time, a manganese‐based anode material is developed and paired up for combining electrocatalytic water oxidation and selective oxygenations of organics delivering the highest efficiency reported to date. This can be achieved by employing helical manganese borophosphates, representing a new class of materials. The uniquely high catalytic activity and durability (over 5 months) of the latter precursors in alkaline media are attributed to its unexpected surface transformation into an amorphous MnOx phase with a birnessite‐like short‐range order and surface‐stabilized MnIII sites under extended electrical bias, as unequivocally demonstrated by a combination of in situ Raman and quasi in situ X‐ray absorption spectroscopy as well as ex situ methods.

Unraveling the Mechanisms of Electrocatalytic Oxygenation and Dehydrogenation of Organic Molecules to Value‐Added Chemicals Over a Ni–Fe Oxide Catalyst

“…It completely vanishes in the postreaction mixture (Figure 7b, blue), suggesting full conversion of the starting HMF. [ 50,51 ] The appearance of a peak at ≈7 ppm indicates its conversion to FDCA (Figure 7b, red). It is stimulating to note that with a current density as high as 25 mA cm −2 , full conversion of HMF with a Faradaic yield of 80% can be achieved.…”

Amorphous Nickel–Iron Borophosphate for a Robust and Efficient Oxygen Evolution Reaction

“…[16] Additionally, these well-developed 1D channels in the borophosphate structure could act as the diffusion path for the ions (e.g., OH− or H+) and water molecules enabling further utilization of the active sites located under the surface of the electrocatalyst. [8,17] LiNiFe-borophosphate (LNFBPO) was synthesized by a facile hydrothermal method. For the comparison purpose, LiNi-borophosphate (LNBPO) was also prepared.…”

Evolving Highly Active Oxidic Iron(III) Phase from Corrosion of Intermetallic Iron Silicide to Master Efficient Electrocatalytic Water Oxidation and Selective Oxygenation of 5‐Hydroxymethylfurfural

“…Considering the observation that, during the OER, most of the usually highly corrosion resistant intermetallic materials transform at least partly to MO x H y phases (M = Fe, Co, Ni), a central research question is to uncover the nature of the newly formed MO x H y phase as it is most likely responsible for the catalytic activity. [ 32,33 ] Recently, it has been shown that the structure of the precursor (e.g., FeSi) and the transformation conditions (e.g., pH or potential) strongly influence the catalytic and chemical properties of the in situ formed catalytically active MO x H y phases. [ 32 ] These considerations explain why MO x H y phases are often more active when they are formed in situ from precursors which contain anions that tend to get oxidized and leach during OER conditions.…”