Self-activated Ni(OH)2 cathode for complete electrochemical reduction of trichloroethylene to ethane in low-conductivity groundwater

This study investigates the electrochemical dechlorination of trichloroethylene (TCE) to non-toxic and value-added ethane by self-activated Ni(OH)2 cathode. The Ni(OH)2 cathode was fabricated by drop-casting the as-synthesized Ni(OH)2 suspensions on a glassy carbon electrode. At −1.0 V applied potential, 94.6% of TCE is reduced after 5 h of electrolysis. TCE is efficiently transformed to ethane at a wide pH range in simulated groundwater environment with low-conductivity. The air-exposed Ni(OH)2 cathode can still dechlorinate 49.8% TCE, showing the antioxidative capacity of Ni(OH)2 cathode is superior than that of pristine Ni electrode. Both the directly transferred electrons and the generated atomic H* at the active Ni(0) sites contributed to the hydrodechlorination of TCE. Our work not only provides an effective way to completely detoxify chlorinated organic contaminants (COCs) under environment-relevant conditions, but also proves a concept that the chemical energy in COCs can be harvested during their electrochemical reduction processes.