Acetic acid (AA), a vital compound in chemical production and materials manufacturing, is conventionally synthesized by starting with coal or methane through multiple steps including high-temperature gasification of coal or steam reforming of CH4 to produce syngas at >800oC, methanol synthesis from syngas at ~300oC and the methanol carbonylation at ~250oC. Here we present a new synthesis of AA at solid-liquid interface from ethane through photocatalytic selective oxidation of ethane by H2O2 at quite low temperature, 0-25°C. By anchoring single-atom Pd1 on g-C3N4, we demonstrated a highly selective and active catalytic method for synthesizing acetic acid from ethane dissolved in aqueous solution at ambient pressure using Pd1/g-C3N4 under light irradiation at 0°C or room temperature. It represents a green synthetic route of AA with minimal energy expenditure and zero environmental impact. At 0°C, the catalyst, Pd1/g-C3N4, exhibits exceptional performance, including a turnover frequency (TOF) of 278 per hour and an exceptionally high selectivity of 98.7% for synthesizing acetic acid. In-situ characterizations and computational simulations revealed that a positively charged single-atom Pd1 site with adsorbed OH, generated under photoirradiation, selectively activates the first C-H bond of C2H6 for AA synthesis through a concerted mechanism with a barrier of only 0.14 eV. By integrating photocatalysis with thermal catalysis, we introduce a highly selective, environmentally friendly, energy-efficient synthetic route for AA, starting from ethane, presenting a promising alternative for AA synthesis. This integration of photocatalysis in low-temperature oxidation demonstrates a new route of selective oxidation of light alkanes. The successful demonstration of selective oxidation of ethane to AA at 0-25oC suggests the significance of integration of photocatalysis to low-temperature oxidation of light alkanes.
