Silicon Carbide Photonic Crystal Photoelectrode

The immense challenge of large-scale implementation of photoelectrochemical (PEC) water splitting and carbon fixation lies in the need for a cheap, durable, and efficacious photocatalyst. Cubic silicon carbide (3C-SiC) holds compelling potential due to its auspicious band positions and high-volume, high-quality, single crystal industrial manufacturing, but is hindered by its inferior light absorptivity and anodic instability. A slanted parabolic pore photonic crystal (spbPore PC) architecture with graphitic carbon nitride (g-CN), nickel(II) oxide (NiO), or 6H silicon carbide protective coatings is proposed to overcome the drawbacks of 3C-SiC photoelectrodes. A 30 µm- and 62 µm-thick 3C-SiC spbPore PC of lattice constant 0.8 µm demonstrates maximum achievable photocurrent density (MAPD) of 9.95 and 11.53 mA cm^-2 in the [280.5, 600] nm region, respectively, representing 75.7% and 87.7% of the total available solar photocurrent density in this spectral range. A 50 nm-thick g-CN or NiO coating forms type-II heterojunctions with the 3C-SiC spbPore PC, facilitating the charge transport and enhancing the corrosion resistivity, all together demonstrating the MAPD of 9.81 and 10.06 mA cm^-2, respectively, for 30 µm-thick PC. The scheme advances the low-cost, sustainable, real-world deployment of PEC cells for green solar fuel production.