Bias-free solar-driven ammonia coupled to C3-dihydroxyacetone production through photoelectrochemistry.

Conversion of solar energy into value-added chemicals through photoelectrochemistry (PEC) holds great potential for advancing sustainable development but limits by high onset potential which affects energy conversion efficiencies. Herein, we utilized a CuPd cocatalyst-modified Sb2(S,Se)3 photocathode (CuPd/TSSS) to achieve an ultra-low onset potential of 0.83 VRHE for photoelectrochemical ammonia synthesis. Meanwhile, we achieved unbiased NH3 production by synthesizing major value-added C3-dihydroxyacetone (DHA) through glycerol oxidation on the BiVO4 photoanode with the loading Pd cocatalyst, instead of a traditional solar water oxidation reaction. The PEC integrated system stably produced 11.98 µmol cm-2 of NH3 and 201.9 mmol m-2 of DHA over 5 h with ~80% faradaic efficiency without applying additional bias. In situ analysis and theoretical calculations confirmed high catalytic activity for ammonia synthesis at the CuPd/TSSS photocathode and enhanced selectivity for DHA at the Pd/BiVO4 photoanode. This design represents a breakthrough in directly utilizing solar energy, nitrate-containing wastewater, and biomass waste for ammonia and highly value-added C3 production, which addresses increasing energy demands while decreasing environmental impact.