Determining Key Parameters of n- and p-Type 3C-SiC Photoelectrodes for Water-Splitting Application

Abstract

Photoelectrochemical water splitting is a promising route to sustainable hydrogen production, but it requires semiconductor electrodes with optimal bandgap, proper band-edge alignment to the water redox potentials, and high corrosion resistance. Cubic silicon carbide (3C-SiC) is a compelling candidate due to its near-ideal bandgap energy and excellent chemical stability. Here, we systematically characterize SiC photoelectrodes comprising of n-type and p-type 3C-SiC thin films grown on Si substrates of matching dopant type. Linear-sweep voltammetry and electrochemical impedance spectroscopy yield the key photoelectrochemical parameters including the flat-band potential and open-circuit potential. Ultraviolet photoelectron spectroscopy and low-energy inverse photoelectron spectroscopy provide the valence-band maximum, conduction-band minimum, Fermi level positions, and bandgap energies. Together, these results elucidate the detailed energy band landscapes for both n- and p-3C-SiC/electrolyte interfaces. The energy diagrams explain the observed behavior with and without illumination, confirming that n-doped 3C-SiC functions as efficient photoanode for oxygen evolution while p-doped 3C-SiC acts as photocathode for hydrogen evolution in neutral aqueous electrolyte. Establishing these quantitative band-edge alignments provides a blueprint for designing durable, bias-free tandem PEC architectures. Given the scalability and stability of SiC, these insights advance pathways toward cost-effective, large-scale green-hydrogen production with a reduced environmental footprint.