Sr‐induced Fermi Engineering of β‐FeOOH for Multifunctional Catalysis

Abstract

Designing a multifunctional electrocatalyst to produce H2 from water, urea, urine, and wastewater, is highly desirable yet challenging because it demands precise Fermi‐engineering to realize stronger π‐donation from O 2p to electron(e−)‐deficient metal (t2g) d‐orbitals. Here a Sr‐induced phase transformed β‐FeOOH/α‐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+(t2g)‐orbitals to e–‐deficient Fe4+(t2g)‐orbitals, via strong π‐donation from the π‐symmetry lone‐pair of O bridge. pt‐NFS utilizes Fe‐sites near the Sr‐atom to break the H─O─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 H2‐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, ≈1.352 V, and ≈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.