Pd doped carbon nitride (Pd-g-C₃N₄): an efficient photocatalyst for hydrogenation via an Al-H₂O system and an electrocatalyst towards overall water splitting

A straightforward and mild protocol for photochemical in situ selective hydrogenation is described via an Al-H₂O system as a hydrogen donor and deploying a Pd-g-C₃N₄ photocatalyst under visible light and ambient conditions. Water, a green solvent, provided hydrogen and the photocatalyst Pd-g-C₃N₄ facilitated hydrogenation with excellent yield and selectivity for a wide range of olefins and nitro compounds (>99%). The robust catalyst is stable with excellent reusability for five consecutive runs. Besides recognition for its excellent photocatalytic ability, Pd-g-C₃N₄ has also been introduced as an efficient bifunctional electrocatalyst towards overall water splitting (both the hydrogen evolution and the oxygen evolution reaction) with excellent durability; it can catalyze both half-cell reactions in the same media (0.5 M H₂SO₄ solution) with Tafel slopes for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) for the catalyst being 36 and 72 mV dec⁻¹, respectively. The enhanced catalytic activities may be due to the synergistic effect among Pd and C and N of the C₃N₄ material. These findings point to a promising pathway to assemble a robust and efficient catalyst for both photochemical and electrochemical reactions and pave a new avenue for the development of a bifunctional photo/electrocatalyst for hydrogenation and overall water splitting.