Puffing quaternary FexCoyNi1-x-yP nanoarray via kinetically controlled alkaline etching for robust overall water splitting

Abstract

Designing and constructing bifunctional electrocatalysts with high efficiency, high stability and low cost for overall water splitting to produce clean hydrogen fuel is attractive but highly challenging. Here we constructed puffed quaternary Fe x Co y Ni 1−x−y P nanoarrays as bifunctional electrodes for robust overall water splitting. The iron was used as the modulator to manipulate the electron density of NiCoP nanoarray, which could increase the positive charges of metal (Ni and Co) and P sites. The resultant electronic structure of Fe x Co y Ni 1−x−y P was supposed to balance the adsorption and desorption of H and accelerate the oxygen evolution reaction (OER) kinetics. Moreover, the morphological structure of Fe x Co y Ni 1−x−y P was modulated through the kinetically controlled alkaline etching by using the amphoteric features of initial FeCoNi hydroxide nanowires. The resultant puffed structure has rich porosity, cavity and defects, which benefit the exposure of more active sites and the transport of mass/ charge. As a result, the cell integrated with the puffed quaternary Fe x Co y Ni 1−x−y P nanoarrays as both the cathode and anode only requires the overpotentials of 25 and 230 mV for hydrogen evolution reaction (HER) and OER at the current density of 10 mA cm −2 in alkaline media and a cell voltage of 1.48 V to drive the overall water splitting. Moreover, the puffed Fe x Co y Ni 1−x−y P demonstrates remarkable durability for continuous electrolysis even at a large current density of 240 mA cm −2 .

Hollow cobalt-nickel phosphide nanocages for efficient electrochemical overall water splitting

“…To maximize the electrochemical performance of the catalysts, endowing the electrocatalysts with hollow nanostructures is regarded as an effective approach, which can significantly increase their specific surface areas and expose more reactive sites [34][35][36][37]. Moreover, the ion diffusion length and transport resistance for water splitting can be effectively reduced by their large void spaces, which has been fully demonstrated by previous studies [38][39][40]. Therefore, the rational design of bimetallic transition-metal phosphides with hollow nanostructures is of great significance for improving their electrocatalyitc activities towards both HER and OER.…”

Corrosive-coordinate engineering to construct 2D-3D nanostructure with trace Pt as efficient bifunctional electrocatalyst for overall water splitting

“…At present, noble metal Pt-and Ru/Ir-based nanomaterials are the benchmark electrocatalysts toward HER and OER [22][23][24][25][26]; however, the high price and scarcity hinder the practical commercialization of water splitting technology [27][28][29][30]. In general, HER and OER electrocatalysts present remarkable electrocatalytic performances in acid and alkaline media, respectively, owing to their favorable reaction kinetics [31,32]. Thus, the mismatched electrocatalysts in the same electrolyte also degrade the electrocatalytic activity and increase the cost accordingly.…”

Synergetic Engineering of High‐Oxidation‐State Cations on Phase Boundaries toward High‐Efficiency Water Splitting

“…The C dl values of Fe‐o‐NiAlOH, Fe‐o‐NiAlOH‐2, and Fe‐o‐NiAlOH‐0.5 are 130.1 mF cm −2 , 63.3 mF cm −2 and 26.4 mF cm −2 , respectively, suggesting the largest surface area of Fe‐o‐NiAlOH. Electrochemical active surface areas (ECSA) of Fe‐o‐NiAlOH, Fe‐o‐NiAlOH‐2, and Fe‐o‐NiAlOH‐0.5 were quantified based on the equation of ECSA=(C dl *A)/C s , where A is the geometric area of working electrode, Cs is a constant whose value is reported to be 0.040 mF cm −2 [56–58] . The ECSA value of Fe‐o‐NiAlOH (813.1 cm 2 ) was significantly higher than those of Fe‐o‐NiAlOH‐2 (395.6 cm 2 ) and Fe‐o‐NiAlOH‐0.5 (165.0 cm 2 ), demonstrating that Fe‐o‐NiAlOH could expose more catalytical active sites for better excellent catalytic activity for OER.…”