Carbon nanofiber/conductive polyaniline-supported neodymium-modified NiAl-LDH as a bifunctional photoelectrocatalyst for water splitting

Water splitting is a promising approach for clean hydrogen production, and its efficiency can be significantly enhanced by rare earth elements (REEs)-doped layered double hydroxides (LDHs) integrated with conductive polymers and carbon derivatives, offering multifunctional benefits for energy and environmental applications. Hence, conductive polyaniline (CSA:PANi) was combined with carbon nanofiber, and neodymium-doped NiAl-LDHs were synthesized at various mole percentages of 0.5–10%. Based on the results from photoelectrochemical (PEC) analysis, the optimal sample for hydrogen and oxygen production was found to be 2%NdNA-LDH nanocomposite as bifunctional photoelectrode. The synthesized 2%NdNiAl-LDH/ CSA:PANi/ Carbon nanofiber (2%NdNAPC_nf) had extremely small overpotentials of 196 mV (hydrogen evolution reaction (HER)) and 195 mV (oxygen evolution reaction (OER)) under dark conditions, and 192 mV (HER) and 167 mV (OER) under illumination, to deliver 10 mA.cm⁻² in alkaline media. Mott-Schottky (M-S) analysis revealed the optimized energy levels in the 2%NdNAPC_nf sample. The electrochemical impedance spectroscopy (EIS) results under both dark and illuminated conditions (4.23 and 2.30 ohm.cm²) indicated its low charge transfer resistance. Stability analysis confirmed the robust electrochemical performance of the 2%NdNAPC_nf under alkaline conditions, demonstrating its promise as a bifunctional photoelectrocatalyst for both HER and OER. The Tafel slopes related to HER and OER for the 2%NdNAPC_nf were obtained as 82.63 and 68.50 mV.dec⁻¹, respectively, indicating optimized reaction kinetics in both processes. Faradaic efficiency (FE) of 2%NdNAPC_nf for hydrogen production achieved about 85 and 78% for alkaline water and NaCl-containing water splitting using hydrogen sensor.