Dinitrosyl iron complexes (DNICs) acting as catalyst for photocatalytic hydrogen evolution reaction (HER)

Abstract

AbstractElectrochemical study of {Fe(NO)2}10 DNIC [(2‐AMP)Fe(NO)2] (1) (2‐AMP = 2‐aminomethylpyridine) in CH3CN/Na2SO4 aqueous solution (1 M) revealing reversible one‐electron redox couples implicated that DNIC 1 may facilitate versatile chemical reactions associated with two‐electron HER (hydrogen evolution reaction) processes. The three‐component photocatalytic HER system is composed of MeOH‐H2O solution (1:1 volume ratio, pH = 11.0) of molecular catalyst DNIC 1 (1.6 μM), photosensitizer fluorescein (Fl) (1.5 mM) and sacrificial electron donor triethylamine (0.36 M) was developed. The reductive quenching rate (R1) (electron transfer from Et3N to Fl) and the oxidative quenching rate (R2) (electron transfer from [Fl]− to DNIC 1) were calculated as 2.11 × 107 s−1 and 3.984 × 104 s−1, respectively. The faster electron transfer from [Fl]− to DNIC 1, compared to the electron‐transfer rate (R3) from [DNIC 1]− to H2O, rationalized the accumulation of the transient‐stable [DNIC 1]−, degrading to [DNIC 1]−‐transformed photocatalytic active particles (Fe3O4 [major]). The three‐component photocatalytic system composed of MeOH‐H2O solution of the isolated particles (2 mg), Fl (1.5 mM), and Et3N (0.36 M) was also employed for photocatalytic HER reaching TON 13456 μmolH2/gcatalyst, TOF 2691 hr−1μmolH2/gcatalyst and the apparent quantum yield 3.71% under radiation (480 nm). That is, for the photocatalytic HER device constructed via a combination of DNIC 1, Fluorescein, and triethylamine, both the homogeneous catalytic HER triggered by {Fe(NO)2}10‐reduced [DNIC 1]− and the heterogeneous catalytic HER promoted by [DNIC 1]−‐transformed particles operated concomitantly to drive this photocatalytic HER.