摘要
Herein, the electrodeposited-film electrode CFeCoNiP was fabricated to serve as a bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Kinetic Tafel slope analysis suggests that the HER follows the Volmer-Tafel mechanism (29 mV dec -1 ), indicating that the recombination of the two adsorbed hydrogen atoms is the rate-determining step. The FeCoNi-based thick film (thickness: 168.3 µm) shows a metallic state favorable for electron transfer; on the other hand, in the case of the FeCoNi-based thin film (thickness: 389.2 nm), the inoperandoXAS investigation reveals that Fe 3+ -assisted water dissociation promotes the formation of Co 2+ -µ-H-Ni 3+ (catalyst-H ad ) species, which subsequently undergoes reductive elimination to furnish H 2 gasviathe HER process. During the OER, the CoNi-oxide matrix acts as a chemical and electroconductive host to build/stabilize the key intermediate [Fe 4+ ?O/Fe 3+ -O?] motifs; this subsequently triggers the catalytic O-O bond formation (30 mV dec -1 ) through the radical-radical coupling of the adjacent [Fe 4+ ?O/Fe 3+ -O?] motifs or/and OH - attack on the Fe 4+ -induced electrophilic oxygen center, leading to the release of O 2 . The mechanistic experiments provide advanced insights into the catalytic kinetics/intermediates and demonstrate that the electronically cooperative interplay among Fe/Co/Ni leads to enhanced alkaline water electrolysis. The CFeCoNiP catalyst exhibits an excellent HER activity (specific activityj s = 0.227 mA cm -2 ) with a low charge transfer resistance (3.9 O) and an overpotential of 37 mV, achieving the current density of 10 mA cm 2 ; moreover, it shows good OER activity (j s = 1.798 mA cm -2 ) with low charge transfer resistance (2.1 O) and an overpotential of 250 mV, approaching a current density of 10 mA cm -2 in a 1 M NaOH aqueous solution. The CFeCoNiP/NF (electrodeposited on Ni foam) electrode-pair device achieved the current densities of 100 and 500 mA cm -2 at the voltages of 1.65 and 1.86 V, respectively, under alkaline conditions.