Integrated halide perovskite photoelectrochemical cells with solar-driven water-splitting efficiency of 20.8.

Achieving high solar-to-hydrogen (STH) efficiency concomitant with long-term durability using low-cost, scalable photo-absorbers is a long-standing challenge. Here we report the design and fabrication of a conductive adhesive-barrier (CAB) that translates >99% of photoelectric power to chemical reactions. The CAB enables halide perovskite-based photoelectrochemical cells with two different architectures that exhibit record STH efficiencies. The first, a co-planar photocathode-photoanode architecture, achieved an STH efficiency of 13.4% and 16.3 h to t60, solely limited by the hygroscopic hole transport layer in the n-i-p device. The second was formed using a monolithic stacked silicon-perovskite tandem, with a peak STH efficiency of 20.8% and 102 h of continuous operation before t60 under AM 1.5G illumination. These advances will lead to efficient, durable, and low-cost solar-driven water-splitting technology with multifunctional barriers.

Fit-for-purpose treatment goals for produced waters in shale oil and gas fields.

Hydraulic fracturing (HF), or "fracking," is the driving force behind the "shale gas revolution," completely transforming the United States energy industry over the last two decades. HF requires that 4-6 million gallons per well (15,000-23,000 m3/well) of water be pumped underground to stimulate the release of entrapped hydrocarbons from unconventional (i.e., shale or carbonate) formations. Estimated U.S. produced water volumes exceed 150 billion gallons/year across the industry from unconventional wells alone and are projected to grow for at least another two decades. Concerns over the environmental impact from accidental or incidental release of produced water from HF wells ("U-PW"), along with evolving regulatory and economic drivers, has spurred great interest in technological innovation to enhance U-PW recycling and reuse. In this review, we analyze U-PW quantity and composition based on the latest U.S. Geographical Survey data, identify key contamination metrics useful in tracking water quality improvement in the context of HF operations, and suggest "fit-for-purpose treatment" to enhance cost-effective regulatory compliance, water recovery/reuse, and resource valorization. Drawing on industrial practice and technoeconomic constraints, we further assess the challenges associated with U-PW treatment for onshore U.S. operations. Presented are opportunities for targeted end-uses of treated U-PW. We highlight emerging technologies that may enhance cost-effective U-PW management as HF activities grow and evolve in the coming decades.

In Situ Methods for Identifying Reactive Surface Intermediates during Hydrogenolysis Reactions: C-O Bond Cleavage on Nanoparticles of Nickel and Nickel Phosphides.

Identifying individual reactive intermediates within the "zoo" of organometallic species that form on catalytic surfaces during reactions is a long-standing challenge in heterogeneous catalysis. Here, we identify distinct reactive intermediates, all of which exist at low coverages, that lead to distinguishable reaction pathways during the hydrogenolysis of 2-methyltetrahydrofuran (MTHF) on Ni, Ni12P5, and Ni2P catalysts by combining advanced spectroscopic methods with quantum chemical calculations. Each of these reactive complexes cleaves specific C-O bonds, gives rise to unique products, and exhibits different apparent activation barriers for ring opening. The spectral features of the reactive intermediates are extracted by collecting in situ infrared spectra while sinusoidally modulating the H2 pressure during MTHF hydrogenolysis and applying phase-sensitive detection (PSD), which suppresses the features of inactive surface species. The combined spectra of all reactive species are deconvoluted using singular-value decomposition techniques that yield spectra and changes in surface coverage for each set of kinetically differentiable species. These deconvoluted spectra are consistent with predicted spectral features for the reactive surface intermediates implicated by detailed kinetic measurements and DFT calculations. Notably, these methods give direct evidence for several anticipated differences in the coordination and composition of reactive MTHF-derived species. The compositions of the most abundant reactive intermediate (MARI) on Ni, Ni12P5, and Ni2P nanoparticles during the C-O bond rupture of MTHF are identical; however, MARI changes orientation from Ni3(µ3-C5H10O) to Ni3(η5-C5H10O) (i.e., lies more parallel with the catalyst surface) with increasing phosphorus content. The shift in binding configuration with phosphorus content suggests that the decrease in steric hindrance to rupture the 3C-O bond is the fundamental cause of increased selectivity toward 3C-O bond rupture. Previous kinetic measurements and DFT calculations indicate that C-O bond rupture occurs on Ni ensembles on Ni, Ni12P5, and Ni2P catalysts; however, the addition of more electronegative phosphorus atoms that withdraw a small charge from Ni ensembles results in differences in the binding configuration, activation enthalpy, and selectivity. The results from this in situ spectroscopic methodology support previous proposals that the manipulation of the electronic structure of metal ensembles by the introduction of phosphorus provides strategies for designing catalysts for the selective cleavage of hindered C-X bonds and demonstrate the utility of this approach in identifying individual reactive species within the zoo.

Microencapsulated Photoluminescent Gold for ppb-Level Chromium(VI) Sensing.

Luminescent gold nanoclusters (Au NCs) are a promising probe material for selective chemical sensing. However, low luminescent intensity and an incomplete understanding of the mechanistic origin of the luminescence limit their practical implementation. We induced glutathione-capped Au NCs to aggregate within silica-coated microcapsular structures using polymer-salt aggregate self-assembly chemistry. The encapsulated NCs have a 5× luminescence enhancement compared to free Au NCs and can detect Cr(VI) at concentrations as low as 6 ppb (=0.12 µM CrO42-) through luminescence quenching, compared to free Au NCs, which have a limit of detection (LOD) of 52 ppb (=1 µM CrO42-). The LOD is 16× lower than the United States Environmental Protection Agency maximum contaminant level for total chromium (Cr(III) + Cr(VI), 100 ppb) in drinking water. No pH adjustment is needed using the encapsulated Au NCs, unlike the case for free Au NCs. The luminescent microcapsule material can sense Cr(VI) in simulated drinking water with a ∼20-30 ppb LOD, serving as a possible basis for a practical Cr(VI) sensor.