Bias-Free Environmental Pollutants Conversion By Integrating Bi-Functional Catalyst with Dual Organic Photoelectrode System

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The rapid increase in human activities has led to an oversupply of nitrate and glycerol, emerging as significant environmental pollutants, disrupting the delicate balance of the global nitrogen and carbon cycles. Addressing this challenge, photoelectrochemical (PEC) conversion harnesses solar energy to effectively convert excess nitrate into ammonia and surplus glycerol into high-value carbon compounds, thereby mitigating their environmental impact and enhancing both environmental sustainability and cost-effectiveness. Notably, among the resulting products, ammonia and formic acid have garnered attention as prominent carriers for hydrogen storage and transportation, given their high hydrogen storage capacity relative to their mass and volume, further emphasizing the importance of PEC conversion. Organic semiconductor materials, characterized by high photovoltage and photocurrent density, present promising prospects for producing efficient photoelectrodes. However, their utility has been hindered by poor stability in aqueous electrolytes. In this study, we address this challenge by employing an encapsulation method to fabricate stable organic semiconductor-based photocathodes and photoanodes operable in aqueous electrolytes. Moreover, we have devised a novel photoelectrochemical system capable of operating without external voltage, facilitated by a dual photoelectrode system. The Ni-Fe-P alloy, with its unique combination of bimetallic and phosphide properties, stands out as a promising non-noble metal catalyst. Nickel facilitates hydrogenation and enhances product selectivity, while iron boosts initial adsorption and reaction activity. Phosphorus disrupts electron distribution, creating additional active sites for intermediate adsorption. This multifaceted catalytic activity enables the Ni-Fe-P alloy to function effectively in both nitrate reduction and glycerol oxidation simultaneously. By integrating a bifunctional Ni-Fe-P catalyst into our dual photoelectrode system, we've achieved significant progress. This system efficiently reduces nitrates and converts glycerol, yielding valuable hydrogen carriers like ammonia and formic acid. Importantly, we've attained photocurrent densities of several mA cm⁻² without the need for bias. This breakthrough marks a robust and effective development in photoelectrochemical systems, addressing both environmental remediation and hydrogen carrier production challenges.