Boosting Hydrogen Adsorption via Manipulating the d-Band Center of Ferroferric Oxide for Anion Exchange Membrane-Based Seawater Electrolysis

Abstract

Ferroferric oxide-based electrocatalysts are widely applied as hydrogen evolution reaction (HER) catalysts due to their low cost and good electrical conductivity, but they tend to exhibit slow hydrogen adsorption kinetics for HER and poison by corrosive Cl − for alkaline seawater splitting. In this regard, we report a nanosheet-like HER catalyst constructed by decorating Fe 3 O 4 with Ru and P dual doping (Ru/P−Fe 3 O 4 @IF). In situ characterization and density functional theory (DFT) calculations demonstrate that the resulting Ru/P−Fe 3 O 4 @IF catalyst shows enhanced hydrogen adsorption strength and hydrogen coverage with a thermal neutral free energy of adsorbed H (ΔG H* ) due to Ru and P dual doping modulating the d-band center of Fe 3 O 4 . Moreover, due to Ru/P doping moving up the d-band center, the weak Cl − adsorption energy makes the poison of Cl − on active sites be avoided in alkaline seawater splitting. Benefiting from the above, the Ru/P−Fe 3 O 4 @IF exhibits superior HER performance to commercial Pt/C in alkaline seawater with overpotentials of only −46 and −144 mV to reach 100 and 1000 mA cm −2 , respectively. In addition, the AEM electrolyzer assembled from Ru/P−Fe 3 O 4 requires only 1.93 V (cell voltage) to drive a current density of 2 A cm −2 and can maintain stable operation for more than 100 h at 500 mA cm −2 for alkaline seawater splitting.