While electrochemical water splitting is one of the most promising methods to store light/electrical energy in chemical bonds, a key challenge remains in the realization of an efficient oxygen evolution reaction catalyst with large surface area, good electrical conductivity, high catalytic properties, and low fabrication cost. Here, a facile solution reduction method is demonstrated for mesoporous Co3O4 nanowires treated with NaBH4. The high‐surface‐area mesopore feature leads to efficient surface reduction in solution at room temperature, which allows for retention of the nanowire morphology and 1D charge transport behavior, while at the same time substantially increasing the oxygen vacancies on the nanowire surface. Compared to pristine Co3O4 nanowires, the reduced Co3O4 nanowires exhibit a much larger current of 13.1 mA cm‐2 at 1.65 V vs reversible hydrogen electrode (RHE) and a much lower onset potential of 1.52 V vs RHE. Electrochemical supercapacitors based on the reduced Co3O4 nanowires also show a much improved capacitance of 978 F g‐1 and reduced charge transfer resistance. Density‐functional theory calculations reveal that the existence of oxygen vacancies leads to the formation of new gap states in which the electrons previously associated with the Co‐O bonds tend to be delocalized, resulting in the much higher electrical conductivity and electrocatalytic activity.

High-performance electrocatalytic CO2 reduction to CO using Ni single-atom catalyst in an anion membrane electrode assembly.

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Shifting electrochemical oxygen reduction towards 2e – pathway to hydrogen peroxide (H 2 O 2 ), instead of the traditional 4e – to water, becomes increasingly important as a green method for H 2 O 2 generation. Here, through a flexible control of oxygen reduction pathways on different transition metal single atom coordination in carbon nanotube, we discovered Fe-C-O as an efficient H 2 O 2 catalyst, with an unprecedented onset of 0.822 V versus reversible hydrogen electrode in 0.1 M KOH to deliver 0.1 mA cm −2 H 2 O 2 current, and a high H 2 O 2 selectivity of above 95% in both alkaline and neutral pH. A wide range tuning of 2e – /4e – ORR pathways was achieved via different metal centers or neighboring metalloid coordination. Density functional theory calculations indicate that the Fe-C-O motifs, in a sharp contrast to the well-known Fe-C-N for 4e – , are responsible for the H 2 O 2 pathway. This iron single atom catalyst demonstrated an effective water disinfection as a representative application.

Earth-abundant Ni single atoms on commercial carbon black were synthesized in large quantities via an economic and scalable protocol, with record-high selectivity and activity toward CO production. Scaling up the electrodes into a 10 3 10-cm 2 modular cell achieves a high overall current over 8 A while maintaining a nearly exclusive CO evolution.

Utilizing solar energy to fix CO 2 with water into chemical fuels and oxygen, a mimic process of photosynthesis in nature, is becoming increasingly important but still challenged by low selectivity and activity, especially in CO 2 electrocatalytic reduction. Here, we report transition-metal atoms coordinated in a graphene shell as active centers for aqueous CO 2 reduction to CO with high faradic efficiencies over 90% under significant currents up to $60 mA/mg. We employed three-dimensional atom probe tomography to directly identify the single Ni atomic sites in graphene vacancies. Theoretical simulations suggest that compared with metallic Ni, the Ni atomic sites present different electronic structures that facilitate CO 2 -to-CO conversion and suppress the competing hydrogen evolution reaction dramatically. Coupled with Li + -tuned Co 3 O 4 oxygen evolution catalyst and powered by a triple-junction solar cell, our artificial photosynthesis system achieves a peak solar-to-CO efficiency of 12.7% by using earth-abundant transition-metal electrocatalysts in a pH-equal system.

Electrochemical reduction of carbon dioxide (CO ) to fuels and chemicals provides a promising solution for renewable energy storage and utilization. Among the many possible reaction pathways, CO conversion to carbon monoxide (CO) is the first step in the synthesis of more complex carbon-based fuels and feedstocks, and holds great significance for the chemical industry. Herein, recent advances in heterogeneous catalysts for selective CO evolution from electrochemical reduction of CO are described. With Au catalysts as a paradigm, principles for catalyst design including size, morphology, and grain boundary densities tuning, surface modifications, as well as metal-support interaction are comprehensively summarized, which shed light on the development of other transition metal catalysts targeting efficient CO -to-CO conversion. In addition, recently emerged novel materials including transition metal single-atom catalysts, which present significantly different catalytic behaviors compared to their bulk counterparts and thus open up many unexpected opportunities, are summarized. Furthermore, the technical aspects with respect to large-scale production of CO are presented, focusing on the full-cell design and implementation. Finally, short comments related to the future direction of real-word CO electrolysis for CO supply are provided in terms of catalyst optimization and technical breakthrough.

Facile interconversion between CO and formate/formic acid (FA) is of broad interest in energy storage and conversion and neutral carbon emission. Historically, electrochemical CO reduction reaction to formate on Pd surfaces was limited to a narrow potential range positive of -0.25 V (vs RHE). Herein, a boron-doped Pd catalyst (Pd-B/C), with a high CO tolerance to facilitate dehydrogenation of FA/formate to CO, is initially explored for electrochemical CO reduction over the potential range of -0.2 V to -1.0 V (vs RHE), with reference to Pd/C. The experimental results demonstrate that the faradaic efficiency for formate (η) reaches ca. 70% over 2 h of electrolysis in CO-saturated 0.1 M KHCO at -0.5 V (vs RHE) on Pd-B/C, that is ca. 12 times as high as that on homemade or commercial Pd/C, leading to a formate concentration of ca. 234 mM mg Pd, or ca. 18 times as high as that on Pd/C, without optimization of the catalyst layer and the electrolyte. Furthermore, the competitive selectivity ηη on Pd-B/C is always significantly higher than that on Pd/C despite a decreases of η and an increases of the CO faradaic efficiency (η) at potentials negative of -0.5 V. The density functional theory (DFT) calculations on energetic aspects of CO reduction reaction on modeled Pd(111) surfaces with and without H-adsorbate reveal that the B-doping in the Pd subsurface favors the formation of the adsorbed HCOO*, an intermediate for the FA pathway, more than that of *COOH, an intermediate for the CO pathway. The present study confers Pd-B/C a unique dual functional catalyst for the HCOOH ↔ CO interconversion.