Supersonically sprayed Zn₂SnO₄/SnO₂/carbon nanotube films for high-efficiency water splitting photoanodes

We demonstrate the supersonic cold-spray deposition of a Zn₂SnO₄/SnO₂/carbon nanotube (CNT) composite as an exceptionally high-performance photoanode for photoelectrochemical water splitting. We optimized the photoanode thickness (number of deposition passes) and composition to achieve a maximum photocurrent density of 17.2 mA cm⁻² at 1.78 V vs. reversible hydrogen electrode, with no additional catalysts or additives. The morphology of the deposited films, as characterized by scanning and transmission electron microscopy, comprises CNTs intermingled with Zn₂SnO₄ and SnO₂ nanoparticles. The high electron concentration and charge transfer rate achieved by adding CNTs are demonstrated through Mott–Schottky and Nyquist analyses of electrochemical impedance spectroscopy (EIS) data. While we find no prior reports of Zn₂SnO₄/SnO₂/CNT nanocomposites for water splitting, we demonstrate that this combination of ball-milled Zn₂SnO₄/SnO₂ nanoparticles mixed with CNTs is a promising candidate for high-performance solar water splitting with dramatically enhanced performance compared to previously-reported ZnO- and SnO-based photoanodes.