In situ construction of porous hierarchical (Ni3-xFex)FeN/Ni heterojunctions toward efficient electrocatalytic oxygen evolution

Abstract

As a choke point in water electrolysis, the oxygen evolution reaction (OER) suffers from the severe electrode polarization and large overpotential. Herein, the porous hierarchical hetero-(Ni 3−x Fe x )FeN/Ni catalysts are in situ constructed for the efficient electrocatalytic OER. X-ray absorption fine structure characterizations reveal the strong Ni-Fe bimetallic interaction in (Ni 3−x Fe x )FeN/Ni. Theoretical study indicates the heterojunction and bimetallic interaction decrease the free-energy change for the rate-limiting step of the OER and the overpotential thereof. In addition, the high conductivity and porous hierarchical morphology favor the electron transfer, electrolyte access and O 2 release. Consequently, the optimized catalyst achieves a low overpotential of 223 mV at 10 mA•cm −2 , a small Tafel slope of 68 mV•dec −1 , and a high stability. The excellent performance of the optimized catalyst is also demonstrated by the overall water electrolysis with a low working voltage and high Faradaic efficiency. Moreover, the correlation between the structure and performance is well established by the experimental characterizations and theoretical calculations, which confirms the origin of the OER activity from the surface metal oxyhydroxide in situ generated upon applying the current. This study suggests a promising approach to the advanced OER electrocatalysts for practical applications by constructing the porous hierarchical metal-compound/metal heterojunctions.

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

“…In recent years, transition-metal oxides and corresponding transition metal phosphides [21][22][23][24], sulfides [25,26], nitrides [27,28], and selenides [29][30][31] have been extensively studied as non-precious bi-functional electrocatalysts for overall water-splitting. In particular, transition metal phosphides, especially bimetallic transition metal phosphides have attracted significant attentions as bi-functional electrocatalysts for water-splitting owing to their remarkably enhanced catalytic activities [32,33].…”

Phosphorus-doped MoS2 with sulfur vacancy defects for enhanced electrochemical water splitting

“…Electrocatalysts can reduce the kinetic overpotential required for the oxygen (OER) and hydrogen (HER) evolution reactions and ultimately improve the efficiency of water decomposition; therefore, these materials are recognized as the most important components of electricity-driven water-splitting technology [10,11]. Although RuO 2 and Pt/C are acknowledged to be the most effective electrocatalysts for the OER and HER, respectively, the commercial applications of these compounds are severely limited by their scarcity and high cost [12][13][14]. Hence, for electrocatalysis, the development of a highly active, naturally abundant, and cost-effective electrocatalyst without noble metal-based compounds is an important subject.…”

Electrocatalytic acidic oxygen evolution reaction: From nanocrystals to single atoms

“…Still, high cost and shortage of provision confine its usage. [ 35 ] In acidic condition, the OER electrocatalysts show less stability and slow reaction kinetics. This behavior occurs due to the slow transfer of electron attached with a proton to the oxygen intermediate species on the catalyst surface.…”