Electrochromism and photocatalysis in dendrite structured Ti:WO3 thin films grown by sputtering

Graphical abstract: - Highlights: • Dendrite structured Ti doped WO₃ (WTO) thin films are grown by co-sputtering. • Sputtering condition influences structure and surface morphology of WTO films. • Titanium doping and annealing lead to dendritic surface structures in WTO films. • Structural, optical, electrochromic and photocatalytic properties of WTO films. • Enhanced electrochromism and photocatalysis in dendrite structured WTO thin films. - Abstract: Titanium doped tungsten oxide (Ti:WO₃) thin films with dendrite surface structures were grown by co-sputtering titanium and tungsten in Ar + O₂ atmosphere. Ti:WO₃ thin films were deposited at oxygen flow rates corresponding to pressures in the range 1.0 × 10⁻³–5.0 × 10⁻³ mbar. Argon flow rate and sputtering power densities for titanium (2 W/cm²) and tungsten (3 W/cm²) were kept constant. Ti:WO₃ films deposited at an oxygen pressure of 5 × 10⁻³ mbar are found to be better electrochromic and photocatalytic. They have high optical modulation (80% at λ = 550 nm), coloration efficiency (60 cm²/C at λ = 550 nm), electron/ion storage and removal capacity (Qc: −22.01 mC/cm², Qa: 17.72 mC/cm²), reversibility (80%) and methylene blue decomposition rate (−1.38 μmol/l d). The combined effects of titanium doping, dendrite surface structures and porosity leads to significant enhancement in the electrochromic and photocatalytic properties of Ti:WO₃ films.