MnO₂ Electrocatalysts Coordinating Alcohol Oxidation for Ultra‐Durable Hydrogen and Chemical Productions in Acidic Solutions

Abstract

Electrocatalytic hydrogen production under acidic conditions is of great importance for industrialization in comparison to that in alkaline media, which, unfortunately, still remains challenging due to the lack of earth‐abundant, cost‐effective and highly active anodic electrocatalysts that can be used durably under strongly acidic conditions. Here we report an unexpected finding that manganese oxide, a kind of common non‐noble catalysts easily soluble in acidic solutions, can be applied as a highly efficient and extremely durable anodic electrocatalyst for hydrogen production from an acidic aqueous solution of alcohols. Particularly in a glycerol solution, a potential of as low as 1.36 V (vs. RHE) is needed at 10 mA cm−2, which is 270 mV lower than that of oxygen evolution reaction (OER), to oxidize glycerol into value‐added chemicals such as formic acid, without oxygen production. To our surprise, the manganese oxide exhibits extremely high stability for electrocatalytic hydrogen production in coupling with glycerol oxidation for longer than 865 hours compared to shorter than 10 h for OER. Moreover, the effect of the addition of glycerol on the electrochemical durability has been probed via in situ Raman spectroscopic analysis and density functional theory (DFT) calculations. This work demonstrates that acid‐unstable metal oxide electrocatalysts can be used robustly in acidic media under the presence of certain substances for electrochemical purposes, such as hydrogen production.

Recent Advances in Electrocatalysts toward Alcohol-Assisted, Energy-Saving Hydrogen Production

“…Li et al reported the use of MnO 2 for selective electro-oxidation of glycerol to produce formic acid in acidic conditions. 83 The MnO 2 showed high stability in 0.5 M H 2 SO 4 for glycerol oxidation coupled with the HER.…”

“…In the complete oxidation of ethanol to CO 2 , the major expected products, such as acetaldehyde and acetic acid, have not been achieved in acidic conditions as yet. Li et al reported the use of MnO 2 for selective electro-oxidation of glycerol to produce formic acid in acidic conditions . The MnO 2 showed high stability in 0.5 M H 2 SO 4 for glycerol oxidation coupled with the HER.…”

Electrochemical Hydrogen Generation by Oxygen Evolution Reaction‐Alternative Anodic Oxidation Reactions

“…Comparatively, overall water splitting in Ni–Mo–N/CFC||Ni–Mo–N/CFC electrolyzer required a higher voltage of 1.62 V to achieve 10 mA cm −2 . The thick MnO 2 /CP NS was synthesized by a facile one‐step electrodeposition method ( Figure a–c), [ 57 ] which reached 10 mA cm −2 at 1.38 V, a much lower voltage compared with 1.78 V required in overall water splitting (Figure 6d,e). The hybrid electrolysis system could realize high stability and nearly 100% FE of H 2 generation.…”

“…e) Time dependences of the electrolyzer voltage over a MnO 2 /CP||Pt/C/CP cell with and without the addition of 0.2 M glycerol at 10 mA cm À2 . Reproduced with permission [57]. Copyright 2021, Wiley-VCH GmbH.…”

An efficient factor for fast screening of high-performance two-dimensional metal–organic frameworks towards catalyzing the oxygen evolution reaction

“…[11][12][13] Hence, designing highly efficient OER materials is a key subject to further improving the application of hydrogen energy technology. [14][15][16][17] Metal-organic frameworks (MOFs) are a kind of porous material formed by the coordination bonds between inorganic metal atoms and organic ligands. 18,19 Due to their unique structural features, MOFs could deliver a series of inherent advantages in heterogeneous catalysis, such as a well-dened chemical structure, large specic surface area and high porosity.…”