A simple chemical solution synthesis of nanowire-assembled hierarchical CuO microspheres with enhanced photochemical properties

A reusable catalyst based on CuO hexapods and a CuO-Ag composite for the highly efficient reduction of nitrophenols

The enormous and urgent need to explore cost-effective catalysts with high efficiency has always been at the forefront of environmental protection and remediation research. This work develops a novel strategy for the fabrication of reusable CuO-based non-noble metal nanomaterials as high-efficiency catalysts. We report a facile and eco-friendly synthesis of CuO hexapods and CuO–Ag composite using uric acid as a reductant and protectant. Both exhibited high catalytic activity in the hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride (NaBH₄), with the CuO–Ag composite showing superior catalytic performance. Notably, the highest turnover frequency of CuO–Ag reached 7.97 × 10⁻² s⁻¹, which was much higher than numerous noble-metal nanomaterials. In addition, CuO hexapods and CuO–Ag composite were also shown to act as highly efficient and recyclable catalysts in the degeneration of 4-NP. Both CuO hexapods and the CuO–Ag composite exhibited outstanding catalytic durability, with no significant loss of activity over more than 10 cycles in the hydrogenation of 4-NP.

Schematic illustration for the process of preparing CuO hexapods and CuO–Ag composite, and their application in catalytically reducing 4-NP and K₃(Fe(CN)₆).

Effect of bandgap alignment on the photoreduction of CO2 into methane based on Cu2O-decorated CuO microspheres

Semiconductors' band gap alignment is important for the photoreduction of CO2 to methane. In the paper, two kinds of Cu2O-decorated CuO microspheres composed with nanoflakes were prepared by using two different methods. Their electron behaviors were studied from the XPS spectra and photoelectrochemical measurements. Both samples are p-type CuO covered with an amount of Cu2O nanoparticles on their surface. Combined with their bandgaps and flat band potentials, CuO-Mic has a well-matched bandgap alignment between Cu2O and CuO, which is favorable for the separation of photogenerated electron-hole pairs. Those photogenerated carriers are beneficial for the conversion of CO2 to CH4, as an 8-electron process for the conversion of CO2 to CH4 will consume more photogenerated electrons for the chemical reactions than that of the 2-electron process for CO2 reduction to CO. Therefore, CuO-Mic has much better photocatalytic activity for CO2 reduction to CH4 with a CH4 yield ten times higher than that of CuO-Hyd under a visible light irradiation, the CO yields of the CO2 reduction are identical.