Sr-induced Fermi Engineering of -FeOOH for Multifunctional Catalysis

Designing a multifunctional electrocatalyst to produce H-2 from water, urea, urine, and wastewater, is highly desirable yet challenging because it demands precise Fermi-engineering to realize stronger pi-donation from O 2p to electron(e(-))-deficient metal (t(2g)) d-orbitals. Here a Sr-induced phase transformed beta-FeOOH/alpha-Ni(OH)(2) catalyst anchored on Ni-foam (designated as pt-NFS) is introduced, where Sr produces plenteous Fe4+ (Fe3+ -> Fe4+) to modulate Fermi level and e(-)-transfer from e(-)-rich Ni3+(t(2g))-orbitals to e(-)-deficient Fe4+(t(2g))-orbitals, via strong pi-donation from the pi-symmetry lone-pair of O bridge. pt-NFS utilizes Fe-sites near the Sr-atom to break the H & horbar;O & horbar;H bonds and weakens the adsorption of *O while strengthening that of *OOH, toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Invaluably, Fe-sites of pt-NFS activate H-2-production from urea oxidation reaction (UOR) through a one-stage pathway which, unlike conventional two-stage pathways with two NH3-molecules, involves only one NH3-molecule. Owing to more suitable kinetic energetics, pt-NFS requires 133 mV (negative potential shift), 193 mV, approximate to 1.352 V, and approximate to 1.375 V versus RHE for HER, OER, UOR, and human urine oxidation, respectively, to reach the benchmark 10 mA cm(-2) and also demonstrates remarkable durability of over 25 h. This work opens a new corridor to design multifunctional electrocatalysts with precise Fermi engineering through d-band modulation.