Scalable decoration of carbonized wood with nickel-iron phosphate-oxyhydroxide as binder-free electrocatalysts for efficient alkaline oxygen evolution reaction

A novel binder-free NiFe-PO 4 -OH electrocatalyst was deposited via the SILAR method at room temperature on three carbonized wood substrates, white pine (PCW), maple (MCW), and cedar (CCW), creating a uniform amorphous mixed-phase combining NiFe oxyhydroxide and metal phosphate phases throughout the microchannel network of the carbonized wood without any thermal treatment. The unique combination of the ordered microchannel architecture of carbonized wood with the amorphous NiFe-PO 4 -OH mixed-phase maximizes electrolyte accessibility, interfacial charge transfer, and long-term coating stability. The systematic comparison of the three wood substrates reveals that their intrinsic structural differences directly govern active phase loading, coating adhesion, and electrocatalytic performance, with NiFe-PO 4 -OH/PCW surpassing both NiFe-PO 4 -OH/MCW and NiFe-PO 4 -OH/CCW across all electrochemical measurements. In 1.0 M KOH, NiFe-PO 4 -OH/PCW achieves at 10 mA cm −2 an overpotential of 248 mV and 73 mV dec −1 in Tafel slope, outperforming IrO 2 . Notably, NiFe-PO 4 -OH/PCW retains more than 95% of its initial current density after 70 h of continuous OER operation, outperforming NiFe-PO 4 -OH/MCW (78.5% after 30 h). With the cathode being Pt/C, NiFe-PO 4 -OH/PCW||Pt/C requires only 1.64 V at 10 mA cm −2 , in a two-electrode configuration. This durability, combined with competitive OER activity and efficient two-electrode water electrolysis, establishes NiFe-PO 4 -OH/PCW as viable low-cost electrocatalysts for sustainable alkaline water splitting.