Robust route to H₂O₂ and H₂ via intermediate water splitting enabled by capitalizing on minimum vanadium-doped...

H₂O₂ is an environmentally friendly chemical for a wide range of water treatments. The industrial production of H₂O₂ is an anthraquinone oxidation process, which, however, consumes extensive energy and produces pollution. Here we report a green and sustainable piezocatalytic intermediate water splitting process to simultaneously obtain H₂O₂ and H₂ using single crystal vanadium (V)-doped NaNbO₃ (V-NaNbO₃) nanocubes as catalysts. The introduction of V improves the specific surface area and active sites of NaNbO₃. Notably, V-NaNbO₃ piezocatalysts of 10 mg exhibit 3.1-fold higher piezocatalytic efficiency than the same catalysts of 50 mg, as more piezocatalysts lead to higher probability of aggregation. The aggregation causes reducing active sites and decreased built-in electric field due to the neutralization between different nano-catalysts. Remarkably, piezocatalytic H₂O₂ and H₂ production rates of V-NaNbO₃ (10 mol%) nanocubes (102.6 and 346.2 µmol·g^-1·h^-1, respectively) are increased by 2.2 and 4.6 times compared to the as-prepared pristine NaNbO₃ counterparts, respectively. This improved catalytic efficiency is attributed to the promoted piezo-response and more active sites of NaNbO₃ catalysts after V doping, as uncovered by piezo-response force microscopy (PFM) and density functional theory (DFT) simulation. More importantly, our DFT results illustrate that inducing V could reduce the dynamic barrier of water dissociation over NaNbO₃, thus enhancing the yield of H₂O₂ and H₂. This facile yet robust piezocatalytic route using minimal amounts of catalysts to obtain H₂O₂ and H₂ may stand out as a promising candidate for environmental applications and water splitting.

Supplementary material (typical Raman spectra of NaNbO₃ and V-NaNbO₃ with various doping concentrations (Fig. S1). XPS spectra of Na 1s (Fig. S2). PL spectra of solution obtained from the piezocatalytic system using NaNbO₃ and V-NaNbO₃ (10 mol%) as the catalysts after 1 h (Fig. S3). The length of NaNbO₃ and V-NaNbO₃ nanocubes calculated from XRD data of their (101) planes (Table S1)) is available in the online version of this article at 10.1007/s12274-022-4506-0.