Multifunctional Coupled Co3O4/CuPc Heterojunction Enables Efficient Photoelectrocatalytic Nitrate-to-Ammonia Conversion

The photoelectrochemical (PEC) reduction of nitrate (NO 3 – ) to ammonia (NH 3 ) offers a sustainable approach for simultaneous wastewater remediation and green NH 3 synthesis. However, current PEC catalysts face limitations in NH 3 conversion efficiency and selectivity, significantly hindering their practical implementation. Herein, we developed a visible-light-responsive heterojunction catalyst composed of Co 3 O 4 nanowires and copper phthalocyanine (CuPc) for selective NO 3 – to NH 3 conversion. The Co 3 O 4 nanowires provide abundant oxygen vacancy (acting as Lewis acid sites) and high surface areas, which synergistically enhance NO 3 – adsorption and activation. Meanwhile, the CuPc coating extends visible-light absorption and effectively suppresses the competing hydrogen evolution reactions (HER). The coherent interface between Co 3 O 4 and CuPc not only promotes efficient charge separation but also stabilizes key reaction intermediates, achieving a 17-fold increase in NH 3 yield (41.2 μg h –1 cm –2 at 0 V vs RHE) compared to pristine Co 3 O 4 . Density functional theory calculations demonstrate reduced energy barriers for the NO 3 – reduction pathway and suppressed HER activity at the heterojunction. This work underscores the potential of interfacial engineering in advancing catalytic systems for sustainable NO 3 – remediation and NH 3 synthesis.