Enhanced simultaneous H₂ and CH₄ generation from formaldehyde using CdS/NiO_x nanorods under visible light

Formaldehyde (HCHO) is a toxic by-product widely generated in industrial processes, presenting significant environmental and health risks. Utilizing solar energy to convert HCHO into hydrogen (H₂) and other clean energy provides a sustainable solution for pollution control and energy demands. In this work, a highly active and low-cost CdS/NiO_x photocatalyst was synthesized in situ and applied for the photocatalytic HCHO decomposition. For the first time, simultaneous generation of H₂ and CH₄ was observed during the photocatalytic decomposition of formaldehyde. The optimal H₂ evolution rate can reach up to 13 mmol·g⁻¹·h⁻¹, with a CH₄ production rate of 175 μmol·g⁻¹·h⁻¹ driven by visible light. The close contact between NiO_x and CdS facilitates rapid charge transfer and separation, leading to exceptional photocatalytic performance. Additionally, an apparent quantum yield (AQY) of 2.4% for H₂ production at 420 nm indicates the high solar energy conversion efficiency of the CdS/NiO_x sample. This study presents a promising approach for the sustainable conversion of harmful formaldehyde into valuable energy resources.