Effect of Proton Transfer on Electrocatalytic Water Oxidation by Manganese Phosphates

Abstract

The effect of proton transfer on water oxidation has hardly been measurably established in heterogeneous electrocatalysts. Herein, two isomorphous manganese phosphates (NH4MnPO4 ⋅ H2O and KMnPO4 ⋅ H2O) were designed to form an ideal platform to study the effect of proton transfer on water oxidation. The hydrogen‐bonding network in NH4MnPO4 ⋅ H2O has been proven to be solely responsible for its better activity. The differences of the proton transfer kinetics in the two materials indicate a fast proton hopping transfer process with a low activation energy in NH4MnPO4 ⋅ H2O. In addition, the hydrogen‐bonding network can effectively promote the proton transfer between adjacent Mn sites and further stabilize the MnIII−OH intermediates. The faster proton transfer results in a higher proportion of zeroth‐order in [H+] for OER. Thus, proton transfer‐affected electrocatalytic water oxidation has been measurably observed to bring detailed insights into the mechanism of water oxidation.

Mechanism of Cations Suppressing Proton Diffusion Kinetics for Electrocatalysis

“…Many fundamental energy‐related processes, such as CO 2 reduction (CO 2 RR), [1] O 2 reduction (ORR), [2] oxygen evolution (OER), [3] and H 2 evolution/oxidation, [4] involve proton transfer. In these reactions, electron transfer driven by the electric field is accompanied by a proton transfer process, which can govern the reaction mechanism [1b] and kinetics [4e, 5] .…”

Rational Design and General Synthesis of High-Entropy Metallic Ammonium Phosphate Superstructures Assembled by Nanosheets

“…Apparently, its structure is composed of sheets of distorted CoO 6 corner-sharing octahedra bridged through the oxygen atoms of the phosphate tetrahedra. These layers are interlinked by hydrogen bonds with NH 4 + cations between the inserted sheets. , In addition, this type of material has the advantages of open-framework solids with large channels and cavities, several active sites, and highly stable structures offered by the P–O covalent bond. , A reasonable combination of metal cations is a necessary condition to obtain the synergistic effect to improve electrochemical energy storage performance. The introduction of other metal ions can not only provide more active sites and improve electrical conductivity but also stabilize the cobalt species. , Therefore, it is particularly important to develop new strategies for the facile fabrication of HE-NPOs· n H 2 O.…”

“…These layers are interlinked by hydrogen bonds with NH 4 + cations between the inserted sheets. 31,32 In addition, this type of material has the advantages of open-framework solids with large channels and cavities, several active sites, and highly stable structures offered by the P−O covalent bond. 33,34 A reasonable combination of metal cations is a necessary condition to obtain the synergistic effect to improve electrochemical energy storage performance.…”

Effects of Group IB Metals of Au/Ag/Cu on Boosting Oxygen Evolution Reaction of Cobalt Hydroxide

“…In recent studies, cobalt‐based compounds in the first‐row transition metal series, such as oxides, [15] hydroxides, [16] hydroxyl oxides, [17] sulfides, [18] phosphides, [19] selenides, [20] and nitrides, [21] have been recognized as good candidates for OER electrocatalysts. In addition, recently reported covalent organic framework (COF) films, [22] manganese phosphate, [23] and metal corrosion porous organic polymers (POPs) [24] have also shown good catalytic activity against OER. Among these materials, cobalt hydroxide (Co(OH) 2 ) is a hopeful catalyst for water splitting since its low price of preparation, large specific surface area, and unique electronic properties [25–27] .…”