Glycolysis is a highly efficient and feasible method to recycle polyethylene terephthalate, a popular plastic with enormous production hence potential recyclable waste. To promote efficiency, investigation for optimal glycolysis conditions attracts much research focus. A literature review on the optimal catalyst amount revealed that an effective catalyst amount existed such that using a larger amount would significantly decrease glycolysis conversion. However, more explanation was needed, and how to enhance efficiency was not discovered for such cases. This study aims to improve the catalytic activity of metal salts by proton H⁺ as an effective co-catalyst that mitigates excess catalysts' adverse effects. Experiments with NaHCO₃ catalyst showed that an appropriate amount of proton H⁺ could increase the yield of bis(2-Hydroxyethyl) terephthalate (BHET) in all investigated conditions where excessive NaHCO₃ had been used. The maximal improvement of 7.2% was observed explicitly with the reaction temperature, time, EG:PET, and NaHCO₃:PET of 192 °C, 4 h, 5.0 (w/w), and 1.0% (w/w), respectively. Fourier transform infrared spectroscopy, gas chromatography-mass spectroscopy, and proton nuclear magnetic resonance spectroscopy were applied, demonstrating the high chemical purity of the obtained BHET product. A reaction mechanism was proposed to explain the dual catalytic activities of NaHCO3 and proton H+, highlighting the potential of using proton H+ to boost the glycolysis efficiency while preventing an adverse drop of the BHET yield in case of applying excessive alkali metal salts.