The timely and effective detection of CO and CH₄ is critical as the explosion and poisoning of them can bring serious potential risks to coal mining. In this study, combining metal oxide semiconductors with noble metals offers a promising route to achieve this target. Hierarchical porous Pd modified In₂O₃ nanoflowers were prepared via two-step hydrothermal method and exhibited dual detection of CO and CH₄ at different temperatures. The material has been characterized by a number of advanced techniques and the results indicate that Pd modified In₂O₃ are hierarchical porous nanoflowers structure consisting of pores of approximately 1.8 nm in size. The sensing properties results show that the Pd modified In₂O₃ based sensor exhibits temperature-dependent dual selectivity detection of CO at 280 ℃ and CH₄ at 340 ℃. In addition, the Pd modified In₂O₃ sensor display higher sensing response of CO (5.824 for 100 ppm) and CH₄ (1.162 for 1000 ppm), fast response and recovery time, as well as good repeatability, which demonstrating the great potential for practical application. Such good gas-sensing performance are mainly attributed to the unique flower-like structure, the presence of porosity on the sample surface, and the catalytic effect of Pd.

Metal nanoparticles and metal oxides promisingly provide different catalytic active sites at their interfaces. Constructing high-density interfaces is essential to maximize synergies. Herein, a Cu–Co₃O₄ nanoparticles interfacial structure produced via pyrolysis and moderate oxidation from metal-organic frameworks has been designed to boost the intrinsic activity. The Cu–Co₃O₄ nanoparticles composites exhibit a turnover frequency of 57.5 min⁻¹ for ammonia borane hydrolysis, far higher than those of monometallic Cu and Co₃O₄ nanoparticles, showing the synergistic effect of Cu and Co₃O₄ nanoparticles at their interface. Density functional theory calculations and in situ Raman spectroscopy reveal the catalytic mechanism of dual active sites, in which Co₃O₄ nanoparticles at Cu–Co₃O₄ interface efficiently bind and activate water molecules and Cu nanoparticles easily activate NH₃BH₃ molecules. This study opens up a new pathway for achieving high-efficiency noble metal-free catalysts for hydrogen generation and other heterogeneous catalysis.