Advanced Trifunctional Electrocatalysis with Cu-, N-, S-Doped Defect-Rich Porous Carbon for Rechargeable Zn–Air Batteries and Self-Driven Water Splitting

Abstract

Fuel cells and water splitting are promising sustainable energy storage and conversion systems that can facilitate the usage of renewable resources and reduce the reliance on fossil fuels. These applications require catalysts to perform the required oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). It would be ideal to use a non-noble metal-based multifunctional catalyst for these reactions. Herein, a new type of porous carbon doped with Cu, N, S was prepared as a trifunctional catalyst for the ORR, OER, and HER from S-rich polyphenylene sulfide (PPS). By oxidatively treating the PPS, we critically prevented high-temperature melting of the precursor. Further, high-temperature pyrolysis using ammonia (NH 3 ) desulfurized and introduced N into the carbon matrix, increasing structural defects and the surface area. By introducing copper during the pyrolysis, the tridoped (Cu, N, S) catalyst was successfully synthesized. The extremely large number of active sites and the local chemical environment enable excellent electrocatalytic performance and stability across ORR, OER, and HER at levels superior or comparable to noble metals. This catalyst was also used as the sole catalyst in Zn−air batteries and overall water splitting to demonstrate excellent performance. This synthesis method can pave the way toward new catalyst design and discovery, enabling more versatile and robust energy applications.

Ultrauniformly Dispersed Cu Nanoparticles Embedded in N-Doped Carbon as a Robust Oxygen Electrocatalyst

“…36 The survey XPS spectra of Cu NPs/N-C-n (Figures 3e and S3a, S3c) detect the 40 The concentration of copper is 5.88 wt % in Cu NPs/N-C-800, which is much lower than the result measured by the ICP-OES test (33.37 wt %), indicating that a higher amount of copper nanoparticles is encapsulated in a graphitic carbon layer and cannot be detected by XPS. 1,41 From the Cu 2p XPS spectra (Figures 3f and S3b, S3d), the electron binding energies of Cu 2p 3/2 and Cu 2p 1/2 are located at 932.8 and 952.5 eV, respectively, demonstrating the presence of Cu 0 in Cu NPs/C-N-800 (Figure 3f). 42 To further understand the valence states of Cu species in the catalysts, X-ray absorption spectroscopy (XAS) was conducted.…”

“…The N 1s XPS spectrum of Cu NPs/N-C-700, −800, and −900 can be fitted into three peaks at 398.8, 400.9, and 402.7 eV, corresponding to pyridinic-N, graphitic-N, and pyridinic-N oxides, respectively (Figure 3d). 1 Among the three samples, Cu NPs/N-C-700 has the highest relative content of pyridinic-N (Table S1), and the pyridinic-N gradually transformed into graphitic-N with the increase in pyrolysis temperature. Pyridinic-N and graphitic-N are effective active sites for improving the catalytic activity of ORR, which is achieved by modulating the electronic structure of adjacent carbon atoms and enhancing the limiting current density, respectively.…”

“…The HRTEM image (Figure 4e) further indicates that Cu NPs were encapsulated in graphitic carbon shells with lattice spaces of 0.233 (Figure 4f) and 0.348 nm (Figure 4g), corresponding to the (111) plane of metallic Cu and the (002) plane of graphitic carbon, respectively. 1,11 The structure with Cu NPs confined in carbon shells can not only suppress the dissolution and agglomeration of the inner Cu NPs in harsh conditions but also boost the electron transfer from the Cu cores to the external graphitic carbon, accelerating the ORR. 46 The homogeneous distribution of C, N, and O elements in Cu NPs/N-C-800 was verified by the HAADF-STEM and elemental mapping images (Figure 4h), while Cu was mainly distributed as dispersed NPs.…”

Construction of MnxCoyO4/Ti electrocatalysts for efficient bifunctional water splitting

“…This excellent catalytic activity is attributed to the unique structure and composition of the catalyst. (1) The Ti mesh has good electrical conductivity, it can reduce the resistance of catalytic system; (2) three-dimensional nanostructures are favorable for directional electron transport;…”

“…With the exploitation of fossil energy reserves and the increasingly serious environmental problems, 1,2 it is urgent to develop clean and sustainable energy to replace the traditional fossil energy. 3,4 Hydrogen energy has many advantages such as high calorific value of combustion, 5 no pollution of combustion products and abundant storage of raw materials; 6,7 therefore, it is considered as an ideal substitute for traditional fossil energy.…”