In this study, we adopt an efficient strategy to replace conventional oxygen evolution reaction with small molecules thermodynamically more readily oxidizable species. Hydrazine, ethanol, glycol and urea can be easily oxidized than oxygen evolution reaction, but the lack of low-cost and efficient small molecules oxidation reaction electrocatalysts places constraints on their development. Herein, a flexible electrode based on cobalt selenide nanosheet arrays supported on carbon fiber paper (CoSe/CFP) is prepared through a two-step approach. The as obtained CoSe/CFP is efficient for small molecules electrooxidation reaction at the anode and hydrogen evolution reaction at the cathode. Due to the easier oxidation of hydrazine than other species, the hydrazine oxidation reaction (HzOR) is investigated in details. An assembled electrolytic cell based on the hydrazine oxidation reaction and hydrogen evolution reaction (HER) electrodes provides a current density of 50 mA cm(-2) at a cell voltage of 0.5 V, long-term durability and 98% Faradaic efficiencies. This novel strategy can greatly lower the imput cell voltage than that under full water splitting (1.6-2.0 V) for cost-effective and energy-saving hydrogen production.