Facile hydrothermal synthesis of melamine-based polymers for photocatalytic hydrogen evolution

Solar photocatalytic hydrogen evolution from water splitting has been recognized as a promising hydrogen production technology, the development of efficient, cheap, and practical new photocatalysts is the key to realizing this technology. Compared with semiconductor photocatalysts, polymeric photocatalysts have emerged due to their high structural diversity and adjustable band gaps. The synthesis process of the polymeric photocatalysts is generally complicated, and the reaction conditions are also harsh (such as oxygen free, using catalyst). In this work, melamine-based polymers (MP-1 and MP-2) were synthesized by a simple one-step hydrothermal method using melamine (MA) and p-phthalaldehyde (PPA) as precursors under air atmosphere without any additives. MP-1 and MP-2 display photocatalytic H₂ evolution from water splitting in the presence of Pt as a co-catalyst and TEOA as a sacrificial hole scavenger. The effect of different structure of polymers on photocatalytic H₂ evolution was discussed. The hydrogen evolution rate of MP-1 is 1784.2 umol·h⁻¹·g⁻¹, distinctly higher than that of MP-2 (1139.8 umol·h⁻¹·g⁻¹). The separation and migration of photoinduced carriers for MP-1 and MP-2 were investigated by electrochemical measurements and PL. It is thought that the imine (–C = N–) structure of MP-1 has a good conjugated system, which could generate more photoinduced electron-hole pairs under light excitation, and the charge migration is also more facile, compared with the aminal structure (–N–C–N–) of MP-2. This study is expected to contribute toward the development of “green hydrogen” using solar photocatalysis over synthetically facile polymeric photocatalysts.