He worked first with Hermann Emil Fischer on the field of organic chemistry, but changed to electrochemistry after his work with Wilhelm Ostwald. He is known for the discovery of an electrosynthetic rearrangement reaction of various alkylated ethyl acetoacetates to form hydrocarbons, now called the Tafel rearrangement, and the Tafel equation, which relates the rate of an electrochemical reaction to the overpotential. He is also credited for the discovery of the catalytic mechanism of hydrogen evolution (the Tafel mechanism). Tafel retired aged 48 due to ill health, but continued to write book reviews until his death.