Tuning d-p hybridization in manganese oxide to accelerate hydrogen transfer in glycerol electrooxidation

Electrochemical water splitting is considered to be the most promising hydrogen production technology, but the sluggish kinetics and high energy consumption in the anodic oxygen evolution reaction limit the large-scale deployment of the technology. Coupling energy-efficient electrooxidation of biomass-derived glycerol and cathodic hydrogen evolution reaction provides a promising strategy for improving the techno-economics of the water electrolysis technology. Herein, by dispersing transition metal elements with weak d-p coupling strength into the MnO2 lattice, the fine tuning of the bioctahedral d-p orbital in MnO2 is successfully realized, which greatly accelerates the hydrogen transfer in glycerol oxidation. In-situ Raman results confirmed that Ni–MnO2 could spontaneously activate glycerol molecules and drive hydrogen transfer to lattice oxygen sites, leading to the occurrence of successive phase transitions (α-MnO2→Mn3O4→MnOOH). Density functional theory (DFT) calculations revealed that the incorporation of Ni broadened the d-orbital and regulated the distribution of p-orbitals near the oxygen Fermi level in the lattice, resulting in a relatively high empty orbital state to facilitate the hydrogen transfer process. The optimal Ni–MnO2 delivered a low potential of 1.16 V vs. RHE to reach 10 mA cm−2, a high FE of 99.7% for formate, and superior durability over 80 h. This work provides new insights into balancing the adsorption and activation of biomass molecules while casting a universal strategy for developing efficient biomass oxidation electrocatalysts.