Fig. 3: Impact of Soret effect on anti-precipitation performance.

a Anti-precipitation performance test of isothermal 20 °C, 40 °C, 60 °C, and non-isothermal 60 °C cases. The insets are the diagrams of salt precipitation in the cathode channel, with salt marked with blue domains and the corresponding temperature conditions with dashed boxes. b Schematic of the Soret effect induced thermal diffusion in non-isothermal cases. The direction of thermal diffusion is determined by the sign of the Soret coefficient (S_T). The mass flux of K⁺ will be from the cold side to the hot side when the sign of S_T is negative, which can effectively reduce the K⁺ concentration and consequently alleviate the salt precipitation. c S_T analysis of various electrolyte types and concentrations. ∇c/c as a function of various temperature differences, with the negative value of the slope representing S_T. d Characterization of mass (red bar) and atom (blue bar) content of K by EDS. The inset diagrams are the K distributions on the cross-section of GDE. e The simulated K⁺ distribution within the MEA electrolyzer with (red line) or without (blue line) Soret effect. In the non-isothermal 60 °C case with a constant current density of 200 mA cm⁻², a K⁺ concentration of 17.3 M serves as a threshold to distinguish the occurrence of salt precipitation. f The relationship between current density and cell voltage (solid line for salting-out free cases and dashed lines for salting-out cases). g Stability test of the MEA electrolyzer in 1 M KOH at a constant current density of 100 mA cm⁻² over 200 h for the non-isothermal 40 °C case (solid red circles are for the anode temperature and solid blue circles are for the cathode temperature). The product composition measurements and anolyte refreshment were performed every 40 h. The photograph of the cathode channel shown on the right side was captured after a 200 h stability test. Source data is provided as a Source Data file.