Effect of electrochemical etching parameters on the morphology and photocatalytic activity of porous 4H-SiC flakes

Porous silicon carbide (SiC), with peculiar chemical modifications, can act as a catalyst that enhances stability, selectivity, and sustainability, offering distinct advantages over conventional oxides and carbon substrates as well as bulk SiC. In particular, the 4H-SiC polytype represents a versatile material platform that connects electronic, photonic, mechanical, and quantum functionalities with exceptional robustness, high thermal conductivity, and chemical inertness. While wet etching methods are largely ineffective due to SiC's chemical resistance, electrochemical etching (ECE) provides a powerful route to fabricate thin membranes and porous structures by exploiting dopant-defined regions. Under anodization in hydrofluoric acid-based electrolytes, crystalline material etching yields diverse pore morphologies—spongy, triangular, chevron, dendritic, sinuous, or columnar—strongly influenced by doping, current density, or carrier photogeneration. In this work, we present an extended study on optimizing ECE conditions to tailor the properties of porous 4H-SiC flakes resulting from the etching of SiC wafers under specific operational conditions. Notably, the different etch mechanisms governing the silicon- and carbon-terminated faces produce distinct porosity profiles and, even more relevant, affect the electronic properties and therefore the photocatalytic activity of the obtained SiC flakes. Accordingly, photocatalytic performances are evaluated by following the degradation of organic dyes in water and bio-reforming processes for hydrogen evolution, validating porous SiC flakes as a promising material for environmental remediation and renewable energy production.