This makes the new bimetallic yolk-shell particles superior to most known nickel–sulfide- and even precious-metal-based electrocatalysts. The new nanoparticles are also very useful for this half reaction.īoth water and urea electrolysis require comparatively low cell voltage (1.544 V or 1.402 V, respectively, at 10 mA cm –2 over 100 hours). Sources of urea could include waste streams from industrial syntheses as well as sanitary sewage. For example, instead of being coupled to the production of oxygen, hydrogen production could be coupled to the oxidation of urea, which requires significantly less energy. To reduce the overall voltage of the electrolysis cell, hybrid electrolysis concepts are also being researched. The material can be used as either an anode or a cathode, and demonstrates high activity and stability in the production of hydrogen and oxygen in the electrolysis of water. Phosphorus doping increases the proportion of Ni 3+ relative to Ni 2+ in the hollow particles and allows for faster charge transfer, causing the electrocatalytic reactions to run faster. These are tiny spheres with a compact core and a porous shell with a space in between-much like an egg whose yolk is surrounded by the egg white and so does not touch the shell. This forms objects called yolk-shell nanoparticles made of phosphorus-doped cobalt–nickel–sulfide (P-CoNi 2S 4). To make the material, nanospheres made of cobalt–nickel–glycerate are subjected to combined hydrothermal sulfidation and gas-phase phosphorization. Alternatives based on abundant, inexpensive metals usually do not work satisfactorily for both half reactions.Ī team led by Shuyan Gao (Henan Normal University, China) and Xiong Wen (David) Lou (Nanyang Technological University, Singapore) has now developed a novel, inexpensive, multifunctional electrode material based on cobalt (Co) and nickel (Ni) for efficient electrocatalytic hydrogen production. However, their large-scale use is impeded by high costs, limited abundance, and low stability.
Catalytically effective electrodes, particularly those based on precious metals, can accelerate the electrochemical processes and improve their energy efficiency. Both half reactions of water electrolysis- hydrogen and oxygen evolution-are unfortunately slow and require a lot of power.