Direct ammonia and dihydroxyacetone production in an unbiased photoelectrochemical cell
Xiaotian Guo, Rui‐Ting Gao, Shijie Ren, Nhat Truong Nguyen, Haojie Chen, Limin Wu, Lei Wang
Abstract
Photoelectrochemical production of ammonia usually suffers from a low solar-to-ammonia efficiency and a high overpotential, which influences the bias-free operation of sustainable photoelectrochemistry. Herein, we realize solar-driven ammonia production from waste nitrate by constructing copper-osmium catalysts deposited on the Sb2(S,Se)3 semiconductor, enabling optimized photo-carrier transport pathways and a beneficial co-adsorption configuration of *NO3-H2O moieties. The photocathode reaches a photocurrent density of 5.6 mA cm−2 at 0 VRHE with a low onset potential of 0.86 VRHE and a Faradaic efficiency of 96.98% at 0.6 VRHE under AM 1.5 G illumination. We further employ glycerol oxidation reaction on ruthenium doped bismuth oxide catalyst decorated on titanium oxide photoanode, requiring an onset potential of 0.3 VRHE to enable bias-free operation. The unbiased photoelectrochemical system shows Faradaic efficiencies of over 97% for ammonia products and above 77% for glycerol oxidation product under AM 1.5 G illumination. The large-sized photoelectrodes maintain a stability for 24 h without noticeable degradation. Our works indicate that unassisted and stable PEC ammonia production is feasible with in situ glycerol valorization using the photoanode and photocathode. Photoelectrochemical production of ammonia faces challenges with low efficiency and high overpotential. Here, the authors report a bias-free system using copper-osmium and ruthenium-based catalysts, coupled with glycerol oxidation, for solar-driven ammonia production.