Trimetallic synergistic optimization of 0D NiCoFe-P QDs anchoring on 2D porous carbon for efficient electrocatalysis and high-energy supercapacitor

Developing multi-functional and low-cost noble-metal-free catalysts such as transition metal phosphides(TMPs)to replace noble-metal is of practical significance for energy conversion and storage.However,the low-durability and the agglomeration phenomenon during the electrochemical process limit their practical applications.Herein,using metal–organic frameworks(MOFs)as the precursor and a combined strategy of gradient temperature calcination and thermal phosphorization,a 0D/2D heterostructure of NiCoFe-P quantum dots(QDs)anchored on porous carbon was successfully developed as highly efficient electrode materials for overall water splitting and supercapacitors.Owing to this distinctive 0D/2D heterostructure and the synergistic effect of multi-metallic TMPs,the NiCoFe-P/C exhibits excellent electrocatalytic activity and durability of HER(87 mV at 10 mA cm^(-2))and OER(257 mV at 100 mA cm^(-2))in the KOH electrolyte.When NiCoFe-P/C is used as the two electrodes of electrolyzed water,only 1.55 V can drive the current density to 10 m A cm^(-2).At the same time,our NiCoFe-P/C possessed extraordinary property for charge storage.In particular,an ultra-high energy density of 100.8 Wh kg^(-1) was achieved at a power density of 900.0 W kg^(-1) for our assembled hybrid supercapacitor device NiCoFe-P/C(2:1)//activated carbon(AC).This work may open a potential way for the design of 0D/2D hybrid multifunctional nanomaterials based on TMPs QDs.

DFT-assisted rational design of CoM_(x)P/CC(M=Fe,Mn,and Ni) as efficient electrocatalyst for wide pH range hydrogen evolution and oxygen evolution

Rational design of highly active transition-metal phosphides for electrocatalyzing overall water splitting in a wide pH range assisted by first-principle calculations can efficiently save the developing cost and hence is quite attractive.Under the guidance of density-functional theory(DFT)calculations that the introduction of dopants(Fe,Mn,and Ni)into CoP could promote the hydrogen evolution reaction(HER)performances,a series of binder-free CoM_(x)P/carbon cloth(CC;M=Fe,Mn,and Ni;x=0,0.05,0.2,0.5,and 1)were fabricated.Both experimental measurements and DFT calculations confirm the electronic modulation of dopants.DFT calculations further reveal that the modulated electronic structure promotes the electronic conductivity,favors the adsorption of key species,and consequently promotes the electrochemical performances.As predicted,the bimetallic phosphides demonstrate excellent HER performances in alkaline,acidic,and alkaline simulated seawater solutions and also deliver excellent oxygen evolution reaction(OER)performances,overwhelming the commercial RuO_(2).Benefiting from the modulated electronic structure and the hierarchical structure with massive CoFe0.05P zero-dimensional(0D)quantum dots anchored on two-dimensional(2D)N-doped porous carbon,CoFe0.05P delivered the best HER in four kinds of electrolytes(ƞ10 of 73 mV in an alkaline simulated seawater solution)and OER in two kinds of electrolytes(ƞ10 of 264 mV in an alkaline solution)with excellent stability of 45 h in the alkaline solution.The assembled CoFe0.05P/CC//CoFe0.05P/CC with the electrodes folded by 180°can still maintain a low cell potential of 1.62 V at 10 mA·cm^(−2).This work proves the feasibility of the reported rational design strategy of developing efficient electrocatalysts for overall water splitting in a wide pH range.