Effect of Proton Transfer on Electrocatalytic Water Oxidation by Manganese Phosphates.

The effect of proton transfer on water oxidation has hardly been measurably established in heterogeneous electrocatalysts. Herein, two isomorphous manganese phosphates (NH 4 MnPO 4  ⋅ H 2 O and KMnPO 4  ⋅ H 2 O) were designed to form an ideal platform to study the effect of proton transfer on water oxidation. The hydrogen-bonding network in NH 4 MnPO 4  ⋅ H 2 O 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 NH 4 MnPO 4  ⋅ H 2 O. In addition, the hydrogen-bonding network can effectively promote the proton transfer between adjacent Mn sites and further stabilize the Mn III -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.