PCCP Blog

Physical Chemistry Chemical Physics (PCCP) Advisory Board members Stefan Grimme, Dage Sundholm and So Hirata, experts in the field of theoretical and computational chemistry, have picked their favourite articles recently published in this area in PCCP. This collection highlights the breadth of theoretical research featured in PCCP.

Theory is an important part of PCCP, which is supported by the theoretical and computational chemists on our Editorial and Advisory Boards. In addition to Professors Grimme, Sundholm and Hirata, these include Carlo Adamo, Vincenzo Barone, Matthais Bickelhaupt, David Clary, Alain Fuchs, Peter Gill, Martin Head-Gordon, Pavel Hobza, Roman Krems, Todd Martinez, Pekka Pyykkö, Joachim Sauer, Berend Smit and Hans-Joachim Werner.

Read our Editor’s choice ‘theory’ selection for free today:

New electron correlation theories for transition metal chemistry
Konrad H. Marti and Markus Reiher
DOI: 10.1039/C0CP01883J

High-dimensional ab initio potential energy surfaces for reaction dynamics calculations
Joel M. Bowman, Gábor Czakó and Bina Fu
DOI: 10.1039/C0CP02722G

Forward–backward semiclassical and quantum trajectory methods for time correlation functions
Nancy Makri
DOI: 10.1039/C0CP02374D

Electronic structure in real time: mapping valence electron rearrangements during chemical reactions
Philippe Wernet
DOI: 10.1039/C0CP02934C

The polymorphism of ice: five unresolved questions
Christoph G. Salzmann, Paolo G. Radaelli, Ben Slater and John L. Finney
DOI: 10.1039/C1CP21712G

Relativity and the mercury battery
Patryk Zaleski-Ejgierd and Pekka Pyykkö
DOI: 10.1039/C1CP21738K

Aromaticity of strongly bent benzene rings: persistence of a diatropic ring current and its shielding cone in [5]paracyclophane
Leonardus W. Jenneskens, Remco W. A. Havenith, Alessandro Soncini and Patrick W. Fowler
DOI: 10.1039/C1CP21950B

Ab initio molecular dynamics simulations of a binary system of ionic liquids
Marc Brüssel, Martin Brehm, Thomas Voigt and Barbara Kirchner
DOI: 10.1039/C1CP21550G

On the physisorption of water on graphene: a CCSD(T) study
Elena Voloshina, Denis Usvyat, Martin Schütz, Yuriy Dedkov and Beate Paulus
DOI: 10.1039/C1CP20609E

A thorough benchmark of density functional methods for general main group thermochemistry, kinetics, and noncovalent interactions
Lars Goerigk and Stefan Grimme
DOI: 10.1039/C0CP02984J

Interlayer interaction and relative vibrations of bilayer graphene
Irina V. Lebedeva, Andrey A. Knizhnik, Andrey M. Popov, Yurii E. Lozovik and Boris V. Potapkin
DOI: 10.1039/C0CP02614J

Demystifying the solvatochromic reversal in Brooker’s merocyanine dye
N. Arul Murugan, Jacob Kongsted, Zilvinas Rinkevicius and Hans Ågren
DOI: 10.1039/C0CP01014F

Microscopic structure and dynamics of air/water interface by computer simulations—comparison with sum-frequency generation experiments
Yanting Wang, Nathan O. Hodas, Yousung Jung and R. A. Marcus
DOI: 10.1039/C0CP02745F

Pseudo Jahn–Teller origin of cis–trans and other conformational changes. The role of double bonds
Pablo Garcia-Fernandez, Yang Liu, Isaac B. Bersuker and James E. Boggs
DOI: 10.1039/C0CP00900H

Intracule functional models. V. Recurrence relations for two-electron integrals in position and momentum space
Joshua W. Hollett and Peter M. W. Gill
DOI: 10.1039/C0CP02154G

Potential energy surfaces for gas-surface reactions
Terry J. Frankcombe and Michael A. Collins
DOI: 10.1039/C0CP01843K

Temperature dependence of crystal growth of hexagonal ice (I_h)
Dmitri Rozmanov and Peter G. Kusalik
DOI: 10.1039/C1CP21210A

A molecular dynamics study of 1,1-diamino-2,2-dinitroethylene (FOX-7) crystal using a symmetry adapted perturbation theory-based intermolecular force field
DeCarlos E. Taylor, Fazle Rob, Betsy M. Rice, Rafal Podeszwa and Krzysztof Szalewicz
DOI: 10.1039/C1CP21342C

Are ab initio quantum chemistry methods able to predict vibrational states up to the dissociation limit for multi-electron molecules close to spectroscopic accuracy?
Péter G. Szalay, Filip Holka, Julien Fremont, Michael Rey, Kirk A. Peterson and Vladimir G. Tyuterev
DOI: 10.1039/C0CP01334J

Computing the inhomogeneous broadening of electronic transitions in solution: a first-principle quantum mechanical approach
Francisco José Avila Ferrer, Roberto Improta, Fabrizio Santoro and Vincenzo Barone
DOI: 10.1039/C1CP22115A

First-principles calculation of electronic spectra of light-harvesting complex II
Carolin König and Johannes Neugebauer
DOI: 10.1039/C0CP02808H

Beyond the Förster formulation for resonance energy transfer: the role of dark states
C. Sissa, A. K. Manna, F. Terenziani, A. Painelli and S. K. Pati
DOI: 10.1039/C1CP21004A

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Urine-powered fuel cells could generate electricity and reclaim essential nutrients directly from human and animal waste, say UK scientists. The development could make wastewater treatment easier and cheaper, and provide an abundant source of locally generated power.

The team, led by Ioannis Ieropolous and John Greenman at the Bristol Robotics Laboratory, developed microbial fuel cells (MFCs) – which use bacteria to break down organic molecules and generate electricity – that could run on the organic molecules found in urine, such as uric acid, creatinine and small peptides. 

Finding the right bacteria to munch these molecules was relatively easy – wastewater treatment plants routinely employ bacteria to do the job. But the crucial point, says Ieropoulos, is that the current processes are energy intensive, whereas the fuel cell approach could turn it into an energy-generating process. Getting the urine on the other hand, required a volunteer. ‘It’s one of us,’ quips Greenman, ‘but we’re not going to say which one.’

The bacteria form a robust biofilm on the anode surface of the fuel cell, and pass electrons to the electrode as they respire and metabolise the fuel molecules in the urine. The team have found that smaller cells have higher energy densities, ‘so we’ve followed a path of miniaturisation and multiplication, building stacks of cells,’ says Ieropoulos. An individual cell can produce a current of 0.25mA for 3 days from 25ml of urine, so stacks of hundreds or thousands of cells could run on the amounts of urine available from homes, farms, or public toilets, for example. ‘Initially we’d probably be targeting local microgeneration,’ says Greenman.

The lack of solids – which could clog up the fuel cells – in urine compared to more general wastewater gives this system a significant advantage, comments Lars Angenent, director of the agricultural waste management lab at Cornell University in Ithaca, US. But, he points out, there are some issues: ‘Firstly, there is a societal question – do people want to separate their urine?’ Although there are modern toilets that can perform the separation, it would require a social change. ‘Then there is the cost issue – they’ve shown it can be done, but will it be economical?’

Angenent observes that some research has moved from fuel cells towards electrolysis of the urea in wastewater to form hydrogen or hydrogen peroxide. These valuable products help balance the device costs. However, as Ieropolous explains, the bacteria in their fuel cell can’t metabolise urea as fuel, so it could be possible to pass the urine first through an electrolytic cell to generate hydrogen, then through the MFC to generate electricity from the other organics.

As well as generating power, the team’s MFCs could help reclaim essential nutrients from waste, adds Greenman. Urine is particularly troublesome in wastewater treatment, since it not only contains organic compounds, but also high levels of nitrogen, phosphorus and potassium. Treatment plants currently expend significant effort and energy removing these elements from wastewater, as releasing them constitutes environmental pollution in the same way as excess fertiliser leaching from agricultural land – it promotes algal blooms that can choke out rivers and waterways.

The fuel cell bacteria could sequester those salts to grow and divide, but in normal urine the balance of nutrients is wrong – there isn’t enough carbon fuel for them to grow fast enough to take up sufficient amounts of the other elements. ‘But if you balance it by adding a cheap carbon source like acetate,’ says Greenman, ‘all the nitrogen, phosphate and potassium is captured into daughter bacteria, which perfuse out of the MFC and can be filtered out and dug back into the ground as fertiliser.’

Phillip Broadwith

Read the paper from Physical Chemistry Chemical Physics:

Urine utilisation by Microbial Fuel Cells; energy fuel for the future
Ioannis Ieropoulos, John Greenman and Chris Melhuish
Phys. Chem. Chem. Phys., 2011
DOI: 10.1039/c1cp23213d