Developing metal phosphide catalysts for selective and high-rate CO2 electroreduction

Abstract

The electrocatalytic reduction of carbon dioxide (CO2) into organic molecules (C2+) offers a promising alternative for addressing climate change and facilitating sustainable energy and chemical production. Despite research efforts dating back to the late 1960s, significant technological and fundamental challenges still need to be addressed in this field. These challenges include enhancing electrocatalytic activity, reducing overpotential, and controlling the selectivity of the produced products, all directly influenced by the catalyst's nature and reaction conditions. In recent studies, a new class of compounds known as metal phosphides (MP) has attracted attention for electrochemical CO2 conversion reactions. These compounds are considered alternatives to noble metals for hydrogen evolution reactions (HER), which compete with the CO2 reduction reaction (CO2RR). However, recent findings indicate that phosphorus in metal phosphides can also promote the formation of unsaturated surface atoms, thereby favoring the dimerization of CO2 molecules on the catalyst surface. Electrochemical studies have shown that metal phosphides exhibit high conductivity and chemical resistance across a wide pH range, showcasing their versatility in working under neutral and alkaline conditions. Although promising, there are few reports on applying metal phosphides for CO2RR in producing desired products. It underscores the need to advance our understanding of the electrocatalytic potential of these materials and elucidate the role of phosphorus in the process. This study intends to fill these knowledge gaps by investigating the electrocatalytic potential of nickel phosphide (NiPx) and copper phosphide (CuPx) in a high-current flow electrochemical system. The proposed supervisor, Prof. Dr. Cao Thang Dihn, possesses expertise in electrochemical cell engineering and process evaluation, making his supervision crucial for the success of this project. By validating the catalytic potential of these materials under extreme conditions, we can expand the range of active catalysts for transforming CO2 into value-added compounds, thereby working towards achieving net-zero carbon emissions, a goal aligned with the 13th Sustainable Development Goal set by the United Nations. The successful execution of this project will be closely linked to the FAPESP process mentioned earlier, which provides resources for developing functional materials and effective electrochemical systems. The catalysts will be synthesized using precipitation methods followed by thermal phosphatization, and they will be applied in an electrochemical flow system with varying potentials and flow rates to optimize the setup. Advanced characterization techniques, including XPS and FTIR, will be employed to study product formation kinetics, while NMR/HPLC and GC will be used to quantify the generated compounds. (AU)