Ni-P nanostructures on flexible paper for morphology effect of nonenzymatic electrocatalysis for urea

This study accounts the controllable design over the structure and morphology of Ni-P nanomaterials directly growing on cellulose paper, and its excellent non-enzymatic electrocatalytic performance to urea. The Ni-P papers were prepared by simple solution soaking and electroless bathing. And the simple experimental steps and mild experimental conditions make it possible for large-scale industrial production, and potential for practical applications. In addition, tuning the pH and concentration of the electroless bath, the Ni-P nanomaterials with different morphologies of nanoflower, nanosheet, nanowire microsphere and microsphere were obtained. The Ni-P nanomaterials impart conductivity to cellulose paper while being potently sensitive to urea owing to its high catalytic activity. Cellulose paper has a large specific area and open macroporous framework which hadn't been damaged during the process of electroless bathing, providing much more activated sites for Ni-P deposition. And the prepared Ni-P papers, as composite materials of cellulose papers loading Ni-P nanomaterials, have high electrocatalytic properties to urea. Comparing the electrochemical behaviors of the four Ni-P paper electrodes with different morphologies, the Ni-P nanoflower paper electrode showed the best electrochemical performance with highest sensitivity of 683.46 μA mM⁻¹ cm⁻² in the low concentration range (0–1 mM) and 1140 μA mM⁻¹ cm⁻² in the high concentration range (1–11 mM), lowest detection limit of 12 μM, shortest response time of 3 s, which may owes to the highest surface area of the Ni-P nanoflower structure. It also has a good stability in room environment remaining 97% after 35 days of storage. Moreover, the electrocatalytic activities of the four Ni-P paper electrodes are ranked as follows: nanoflower > nanosheet > nanowire microsphere > microsphere. What's more, the long-term stability and repeatability, good selectivity of the flexible Ni-P paper make it successfully applied to swimming pool water quality monitoring.