NON-PRECIOUS METAL ELECTROCATALYSTS FOR THE OVERALLWATER SPLITTING: SYNTHESIS, CHARACTERIZATION AND PROPERTIES

Developing highly efficient and stable electrocatalysts from inexpensive and earth-abundant elements represents a significant advancement in the overall water splitting (OWS) process. This study investigates the synthesis, characterization, and electrocatalytic properties of four different electrocatalysts: cobalt-phosphorus (CoP), cobalt-iron-phosphorus (CoFeP), palladium-cobalt-phosphorus (PdCoP), and palladium-cobalt-iron-phosphorus (PdCoFeP). The CoP and CoFeP coatings were synthesized using the electroless deposition method, ensuring uniform deposition of metal and phosphorus components on the copper surface. Sodium hypophosphite (NaH\(_{2}\)PO\(_{2}\)) was utilized as the reducing agent. In addition, Pd crystallites were incorporated onto the CoP and CoFeP coatings via the galvanic displacement method, which resulted in a significant enhancement of the catalytic properties. The electrocatalysts were comprehensively characterized through techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and inductively coupled plasma optical emission spectroscopy (ICP-OES). These methods were employed to investigate the surface morphology, structure, and composition of the catalytic materials. The electrocatalytic performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was evaluated in 1 M KOH using a three-electrode setup. Meanwhile, the OWS performance was measured in a two-electrode system. It was found that Pd-modified CoP and CoFeP coatings exhibited superior bifunctional catalytic activities in comparison with CoP and CoFeP, with low overpotentials and high current densities for both HER and OER. The PdCoFeP catalyst demonstrated the lowest overpotential of 180 mV for HER at a current density of 10 mA cm\(^{-2}\) and 398 mV for OER at the same current density, thus exhibiting superior performance in comparison to other compositions. The enhanced performance of PdCoFeP can be attributed to the synergistic effect between Pd, Co, and Fe, which has been shown to enhance charge transfer kinetics and increase the density of active sites. Furthermore, when PdCoFeP electrodes are employed as both the anode and the cathode for water splitting, a low cell voltage of 1.70 V at 10 mA cm\(^{-2}\) is observed. The findings of this study highlight the potential of these phosphide-based materials as promising candidates for sustainable hydrogen production through overall water splitting. This research was funded by a grant (No. P-MIP-23-467) from the Research Council of Lithuania.