Integrated self-powered hydrogen generation enabled by accelerated formaldehyde electrooxidation

The electrocatalytic formaldehyde oxidation (FOR) into H 2 and formate at low potential (<0.5 V vs. RHE) is a promising alternative to lower the energy consumption of water electrolysis to produce renewable hydrogen. In this study, a hybrid copper-based catalyst Pd-Cu 2 O-CuCl with significant catalytic activity was developed for FOR. The strong electronic interaction between CuCl and Cu 2 O regulates the d-band structure and favors the adsorption of intermediates. Moreover, Pd clusters activate C–H bond, thereby facilitating the dehydrogenation step. As a result, remarkably high current density of 390 mA cm −2 is achieved at a low potential of 0.5 V. The much accelerated FOR enables the integration of a direct formaldehyde fuel cell with a bipolar hydrogen production system into a self-powered hydrogen production system, which requires no external power supply. The system produces hydrogen in three out of four electrodes, delivering an overall hydrogen production rate of 13.28 mmol h −1 cm −2 with system-level Faradaic efficiency of 300%, and exceptional stability over 120 h. This work provides new insights into the design of highly performed FOR catalysts and a viable pathway toward self-powered hydrogen generation.