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

ABSTRACT

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. Electronic Supplementary Material: 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.