Active Sites Implanted Carbon Cages in Core–Shell Architecture: Highly Active and Durable Electrocatalyst for Hydrogen Evolution Reaction

Abstract

Low efficiency and poor stability are two major challenges we encounter in the exploration of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) in both acidic and alkaline environment. Herein, the hybrid of cobalt encapsulated by N, B codoped ultrathin carbon cages (Co@BCN) is first introduced as a highly active and durable nonprecious metal electrocatalysts for HER, which is constructed by a bottom-up approach using metal organic frameworks (MOFs) as precursor and self-sacrificing template. The optimized catalyst exhibited remarkable electrocatalytic performance for hydrogen production from both both acidic and alkaline media. Stability investigation reveals the overcoating of carbon cages can effectively avoid the corrosion and oxidation of the catalyst under extreme acidic and alkaline environment. Electrochemical active surface area (EASA) evaluation and density functional theory (DFT) calculations revealed that the synergetic effect between the encapsulated cobalt nanoparticle and the N, B codoped carbon shell played the fundamental role in the superior HER catalytic performance.

Design Strategies toward Advanced MOF‐Derived Electrocatalysts for Energy‐Conversion Reactions

“…[58,60] For instance, in order to fabricate N-doped MOF-derived materials, zeolitic imiazolate frameworks (ZIFs), a subclass of MOFs composed of tetrahedrally coordinated transition metal ions (e.g., Zn, Fe, Co, Cu) and imidazolate (IM) ligands, are frequently utilized as the precursor and/or template because of their high N content and other preferred properties, such as large surface area and uniform particle size. [24,33,34,36,[38][39][40][41]44,53,[64][65][66][67][68][69] Recently, You et al reported the conversion of ZIF-67 (Co(MIM) 2 , MIM = methylimidazole) to Co-and N-doped carbon (CoNC) via direct pyrolysis, producing a N-doped material with high N content. [39] Similarly, Chen and co-workers studied porous carbon materials derived from a series of bimetallic ZIFs (BMZIFs), which are based on ZIF-8 and ZIF-67 with varied Zn/Co ratio.…”

“…[22,59,61,62,64,74,78,79] During the past decade, synergistic coupling effects by the chemical substitution of some carbon atoms with two or more different kinds of heteroatoms have been shown. This is because the co-doping of two or more elements with reverse electronegativity into the carbon matrix can induce unique electron-donor properties.…”

“…[22,79] In the case of MOFderived electrocatalysts, dual and ternary heteroatom doping strategies have also been explored by performing N doping together with one or two other elements (e.g., B, S, and P). [59,61,62,64,74] Therefore, multiple heteroatom doping can be another feasible solution for optimizing the composition of MOF-derived electrocatalysts. Morever, other heteroatoms can be doped through similar strategies to N doping.…”

“…[64] Figure 2d depicts the preparation process for Co@BCN. It can be seen that the bottom-up strategy involves two calcination steps using ZIF-67 and H 3 BO 3 as the precursors.…”

“…[40,53,64,68,70,77,80] Since the metal ions distribute homogeneously among the framework, most of the generated transition metal NPs are encapsulated by the carbon materials. According to previous literature, metal NPs alone display minimal electrocatalytic activity toward energy-conversion reactions.…”