Jiao Lifang research group of Nankai University: "the three-dimensional array has a long service life, with a lot of branches and leaves supporting catalysis"

Hydrogen energy is considered as the ideal energy in the future because of its high calorific value and environmental friendliness So far, large-scale hydrogen production mainly depends on the consumption of fossil fuels, which seriously pollutes the environment As an old hydrogen production technology, electrolytic water hydrogen production is widely favored However, at present, large-scale electrolytic water hydrogen production is limited by the use of expensive noble metal catalysts to reduce the reaction energy barrier, which makes this technology has not been widely used In order to alleviate the increasingly serious energy and environmental problems, the development of non precious metal electrolyzed water catalyst with excellent performance and low price has become a research hotspot Jiao Lifang research group of Nankai University has made some progress in the structural design and performance optimization of non noble metal electrocatalysts (nano letters 2017, 17, 7989; energy storage materials 2018, 12, 44; electrochemista Acta 2019, 298, 305) Cobalt based phosphide is a kind of catalyst for hydrogen precipitation in a wide pH range It has platinum like catalytic activity especially in acid electrolyte Because the total effect exists in the crystal surface of phosphide, the interaction between metal and phosphorus enables it to effectively adsorb protons and desorb the hydrogen molecules formed However, in alkaline water electrolysis, due to the proton comes from the dissociation of water, and the phosphide itself can not effectively promote the dissociation, so its performance under alkaline conditions is often not ideal In order to speed up the dissociation process, the introduction of some compounds with affinity to oxygen-containing functional groups, such as some oxygen precipitation catalysts, can effectively reduce the energy barrier of the dissociation reaction But at the same time, it should be noted that the introduction of non active components may block some active sites, resulting in the degradation of their hydrogen evolution performance; in addition, such components with the characteristics of oxygen adsorption often have poor conductivity, which undoubtedly brings new challenges to the structural design of catalytic electrode In view of the above problems, recently, Professor Jiao Lifang's research group of Nankai University reported a novel bifunctional electrocatalyst with "branch leaf structure", which is composed of one-dimensional crystal cobalt phosphide nanowire ("branch") and two-dimensional amorphous nickel iron hydroxide nano sheet ("leaf") Compared with single component powder electrocatalyst, the catalyst reported in this paper has the following advantages: (1) there is synergistic catalysis between crystalline cobalt phosphide nanowires and amorphous nickel iron hydroxide, which accelerates the reaction kinetics of hydrogen and oxygen precipitation (2) Different from the previously reported "core-shell structure", the hierarchical "branch leaf structure" makes the internal and external components fully exposed in the electrolyte, which not only provides more catalytic active sites, but also greatly accelerates the mass transfer process (3) Cop @ NiFe Oh with metalloid characteristics can induce electron transfer to the active site rapidly (4) The self-supporting electrode configuration not only simplifies the electrode preparation process, but also ensures its stability under high current Combined with the above advantages, the cop @ NiFe Oh electrode with "branch leaf structure" can generate 20 mA cm-2 hydrogen evolution current and oxygen evolution current with only 118 MV and 220 MV overpotential under alkaline conditions, respectively Its performance is better than that of cop and NiFe Oh electrode with single component At the same time, the dual-function cop @ NiFe Oh electrode can generate 10 Ma cm-2 current with a cell voltage of 1.53 V in the whole water electrolysis test and has a stability of up to 120 hours It is one of the best two-component all water electrolysis catalysts so far This work provides a new research idea for the structure design and component coordination of the multi-element nano electrocatalyst The results of "branch leaf structure" bifunctional cop @ NiFe Oh electrocatalyst (source: nano energy) were published on nano energy (nano energy 2019, 63, 103821), which was supported by NSFC.