| As a new-generation energy carrier,hydrogen plays a crucial role in the energy transition process for the merits with large energy density,renewability and environmental friendliness.Electrochemical water splitting is one of the most ideal sustainable approaches for hydrogen production.In order to further improve the energy conversion efficiency of the hydrogen production process from electrochemical water splitting,it is of practical significance to develop electrocatalytic materials with high catalytic activity and low cost.Among non-noble metal materials,transition metal phosphides(TMPs)with special structures exhibit relatively good catalytic performance for electrochemical water splitting.Compared with traditional electrocatalytic materials in the form of powders,self-supported catalytic electrodes make the catalytically active materials expose more active sites,and the binding between the catalytically active materials and the conductive substrates is more tight,so that self-supported electrodes show better catalytic activity and stability.Due to the outstanding electrical conductivity,good chemical stability and mechanical properties,carbon materials are able to be utilized as the conductive substrates for catalytic electrodes.In this paper,three kinds of TMPs/carbon materials composite self-supported electrodes were designed and prepared by using transition metal(Co and W)phosphides and carbon materials with special macroscopic morphologies as the catalytically active materials and the macrostructure skeletons,respectively.All of them exhibited ideal catalytic performance for hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in electrochemical water splitting.The study of this paper is mainly composed of the following three parts(a)Amorphous Co-W-P was deposited on the carbon cloth(CC)by chemical deposition to form the Co-W-P/CC self-supported catalytic electrode material.Co-W-P nanoparticles aggregated to form the nodular structure on the surface of CC.Thus the catalytic performance of Co-W-P/CC for electrochemical water splitting was analyzed in 1.0 M KOH aqueous solution.The overpotentials of Co-W-P/CC are 150 mV for HER and 350 mV for OER at the current densities of-10 mA·cm2 and 10 mA.cm-2,respectively.The two-electrode electrolzer constructed by Co-W-P/CC-3 showed the cell voltage(EOP)of 1.74 V at jcell=10 mA·cm-2,which increased by 2.8%after 20 h testing for electrochemical water splitting(b)The in-situ synthesis of CoWO4/CoP2 nanocomposites on carbon nanotube film(CNTF)was realized by a simple hydrothermal method.The CoP2 was embedded in the interior of CoWO4 in the nanocomposites.CoWO4/CoP2 nanocomposites appeared as nanoflakes and nanoparticles on the surface and inside of carbon nanotubes(CNTs)which make up CNTF,respectively.The formed self-supported catalytic electrode material of CoWO4/CoP2/CNTF exhibited excellent catalytic activity in electrochemical water splitting(1.0 M KOH aqueous solution).The overpotentials of CoWO4/CoP2/CNTF were 133 mV@-10 mA·cm-2 for HER and 252 mV@10 mA·cm-2 for OER,respectively.The Eop of two-electrode electrolzer constructed by CoWO4/CoP2/CNTF was 1.605 V at jcell=10 mA·cm-2.Benefiting from the tight binding between CoWO4/CoP2 and CNTF and the protection of carbon nanotubes’ wall for CoWO4/CoP2 nanoparticles,CoWO4/CoP2/CNTF showed considerable catalytic stability with the only increase by 1.1%of EOP at jcell 10 mA·cm-2 after 32 h testing for continuous electrochemical water splitting.In addition,CoWO4/CoP2/CNTF could also quickly catalyze the reduction of p-nitrophenol(4-NP)to p-aminophenol(4-AP),so it also has certain application potential in the treatment of water pollutants.(c)The in-situ growth of nitrogen,phosphorus doped carbon nanotubes(NPCNTs)encapsulating CoP/WP composite nanoparticles on CC was realized through the multi-step process of solvothermal-CVD-phosphating to construct CoP/WP@NPCNTs/CC self-supported catalytic electrode material.The bamboo-like NPCNTs were uniformly grown or distributed on CC,and CoP/WP composite nanoparticles were dispersed on the top and inside of NPCNTs.CoP/WP@NPCNTs/CC exhibited more outstanding activity and stability in electrochemical water splitting.The overpotentials of CoP/WP@NPCNTs/CC were 88 mV@-10 mA·cm-2 for HER and 185 mV@10 mA.cm-2for OER,respectively,and the corresponding Tafel slopes were 79.44 mV·dec-1 and 72.28 mV·dec-1,respectively.The Eop of the two-electrode electrolzer constructed by CoP/WP@NPCNTs/CC was 1.522 V at jcell=10 mA·cm-2 and its increase was less than 1%after 50 h operation of continuous electrochemical water splitting. |
PDF Full Text Request